Wash liquids for use in additive manufacturing with dual cure resins

ABSTRACT

A method of forming a three-dimensional object, which method includes a cleaning or washing step, is carried out by: (a) providing a carrier and a fill level, and optionally an optically transparent member having a build surface defining the fill level, the carrier and the fill level having a build region therebetween; (b) filling the build region with a polymerizable liquid, the polymerizable liquid comprising a mixture of (i) a light polymerizable liquid first component, and (ii) a second solidifiable component that is different from the first component; (c) irradiating the build region with light, to form a solid polymer scaffold from the first component and also advancing the carrier away from the build surface to form a three-dimensional intermediate having the same shape as, or a shape to be imparted to, the three-dimensional object and containing the second solidifiable component carried in the scaffold in unsolidified and/or uncured form; (d) washing the three-dimensional intermediate; and (e) concurrently with or subsequent to the irradiating step, and/or the washing step, solidifying and/or curing the second solidifiable component in the three-dimensional intermediate to form the three-dimensional object.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/356,911, filed Nov. 21, 2016, which in turn claims the benefit ofU.S. Provisional Patent Application Ser. No. 62/270,728, filed Dec. 22,2015, the disclosure of which is incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The present invention concerns materials, methods and apparatus for thefabrication of solid three-dimensional objects from liquid materials,and objects so produced.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. In particular, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Two techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object.

If new layers are formed at the top surface of the growing object, thenafter each irradiation step the object under construction is loweredinto the resin “pool,” a new layer of resin is coated on top, and a newirradiation step takes place. An early example of such a technique isgiven in Hull, U.S. Pat. No. 5,236,637, at FIG. 3. A disadvantage ofsuch “top down” techniques is the need to submerge the growing object ina (potentially deep) pool of liquid resin and reconstitute a preciseoverlayer of liquid resin.

If new layers are formed at the bottom of the growing object, then aftereach irradiation step the object under construction must be separatedfrom the bottom plate in the fabrication well. An early example of sucha technique is given in Hull, U.S. Pat. No. 5,236,637, at FIG. 4. Whilesuch “bottom up” techniques hold the potential to eliminate the need fora deep well in which the object is submerged by instead lifting theobject out of a relatively shallow well or pool, a problem with such“bottom up” fabrication techniques, as commercially implemented, is thatextreme care must be taken, and additional mechanical elements employed,when separating the solidified layer from the bottom plate due tophysical and chemical interactions therebetween. For example, in U.S.Pat. No. 7,438,846, an elastic separation layer is used to achieve“non-destructive” separation of solidified material at the bottomconstruction plane. Other approaches, such as the B9Creator™3-dimensional printer marketed by B9Creations of Deadwood, S. Dak. USA,employ a sliding build plate. See, e.g., M. Joyce, US Patent App.2013/0292862 and Y. Chen et al., US Patent App. 2013/0295212 (both Nov.7, 2013); see also Y. Pan et al., J. Manufacturing Sci. and Eng. 134,051011-1 (October 2012). Such approaches introduce a mechanical stepthat may complicate the apparatus, slow the method, and/or potentiallydistort the end product.

Continuous processes for producing a three-dimensional object aresuggested at some length with respect to “top down” techniques in U.S.Pat. No. 7,892,474, but this reference does not explain how they may beimplemented in “bottom up” systems in a manner non-destructive to thearticle being produced, which limits the materials which can be used inthe process, and in turn limits the structural properties of the objectsso produced.

Southwell, Xu et al., US Patent Application Publication No.2012:0251841, describe liquid radiation curable resins for additivefabrication, but these comprise a cationic photoinitiator (and hence arelimited in the materials which may be used) and are suggested only forlayer by layer fabrication.

Velankar. Pazos. and Cooper, Journal of Applied Polymer Science 162,1361 (1996), describe UV-curable urethane acrylates formed by adeblocking chemistry, but they are not suggested for additivemanufacturing, and no suggestion is made on how those materials may beadapted to additive manufacturing.

Accordingly, there is a need for new materials and methods for producingthree-dimensional objects by additive manufacturing that havesatisfactory structural properties.

SUMMARY OF THE INVENTION

Described herein are methods, systems and apparatus (includingassociated control methods, systems and apparatus), for the productionof a three-dimensional object by additive manufacturing. In preferred(but not necessarily limiting) embodiments, the method is carried outcontinuously. In preferred (but not necessarily limiting) embodiments,the three-dimensional object is produced from a liquid interface. Hencethey are sometimes referred to, for convenience and not for purposes oflimitation, as “continuous liquid interface production,” “continuousliquid interphase printing,” or the like (i.e., “CLIP”).

The present invention provides a method of forming a three-dimensionalobject, comprising: (a) (i) providing a carrier and an opticallytransparent member having a build surface, the carrier and the buildsurface defining a build region therebetween, or (ii) providing acarrier in a polymerizable liquid reservoir, the reservoir having a filllevel, the carrier and the fill level defining a build regiontherebetween: (b) filling the build region with a polymerizable liquid,the polymerizable liquid comprising a mixture of: (i) a lightpolymerizable liquid first component, and (ii) a second solidifiable (orsecond reactive) component different from the first component; (c)irradiating the build region with light (through the opticallytransparent member when present) to form a solid polymer scaffold fromthe first component and advancing (e.g., advancing concurrently—that is,simultaneously, or sequentially in an alternating fashion withirradiating steps) the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object and containing the secondsolidifiable component carried in the scaffold in unsolidified oruncured form; and (d) concurrently with or subsequent to the irradiatingstep, solidifying and/or curing (e.g., further reacting, polymerizing,or chain extending) the second solidifiable or reactive component in thethree-dimensional intermediate to form the three-dimensional object.

Optionally, a wash step may be included between formation of thethree-dimensional intermediate and the subsequent solidifying and/orcuring step (d) which by which the three-dimensional object is formed.Any suitable wash liquid may be employed (e.g., BIO-SOLV™ solventreplacement; PURPLE POWER™ degreaser/cleaner; SIMPLE GREEN® all purposecleaner; a 50:50 volume:volume mixture of water and isopropanol, etc.See also, U.S. Pat. No. 5,248,456).

In some embodiments, the second component comprises: (i) a polymerizableliquid solubilized in or suspended in the first component; (ii) apolymerizable solid solubilized in the first component; or (iii) apolymer solubilized in the first component. In other embodiments, thesecond component comprises: (i) a polymerizable solid suspended in thefirst component; or (ii) solid thermoplastic or thermoset polymerparticles suspended in the first component.

In some embodiments, the first component comprises a blocked or reactiveblocked prepolymer and (optionally but in some embodiments preferably) areactive diluent, and the second component comprises a chain extender.The first components react together to form a blocked polymer scaffoldduring the irradiating step, which is unblocked by heating or microwaveirradiating during the second step to in turn react with the chainextender. In some embodiments, the reactive blocked component comprisesa reactive blocked diisocyanate and/or chain extender, alone or incombination with a reactive blocked prepolymer, and other unblockedconstituents (e.g., polyisocyanate oligomer, diisocyanate, reactivediluents, and/or chain extender).

In some embodiments, reactive blocked blocked prepolymers,diisocyanates, and/or chain extenders are blocked by reaction of (i.e.,are the reaction product of a reaction between) a polyisocyanateoligomer, a diisocyanate, and/or a chain extender with an amine(meth)acrylate, alcohol (meth)acrylate, maleimide, or n-vinylformamidemonomer blocking agent.

In some embodiments, the three-dimensional intermediate is collapsibleor compressible (e.g., elastic).

In some embodiments, the scaffold is continuous; in other embodiments,the scaffold is discontinuous (e.g., an open or closed cell foam, whichfoam may be regular (e.g., geometric, such as a lattice) or irregular).

In some embodiments, the three-dimensional object comprises a polymerblend (e.g., an interpenetrating polymer network, asemi-interpenetrating polymer network, a sequential interpenetratingpolymer network) formed from the first component and the secondcomponent.

In some embodiments, the polymerizable liquid comprises from 1, 2 or 5percent by weight to 20, 30, 40, 90 or 99 percent by weight of the firstcomponent; and from 1, 10, 60, 70 or 80 percent by weight to 95, 98 or99 percent by weight of the second component (optionally including oneor more additional components). In other embodiments, the polymerizableliquid comprises from 1, 2 or 5 percent by weight to 20, 30, 40, 90 or99 percent by weight of the second component; and from 1, 10, 60, 70 or80 percent by weight to 95, 98 or 99 percent by weight of the firstcomponent (optionally including one or more additional components).

In some embodiments, the solidifying and/or curing step (d) is carriedout concurrently with the irradiating step (c) and: (i) the solidifyingand/or curing step is carried out by precipitation; (ii) the irradiatingstep generates heat from the polymerization of the first component in anamount sufficient to thermally solidify or polymerize the secondcomponent (e.g., to a temperature of 50 or 80 to 100° C., forpolymerizing polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)); and (iii) the second component (e.g., a light orultraviolet light curable epoxy resin) is solidified by the same lightas is the first component in the irradiating step.

In some embodiments, the solidifying and/or curing step (d) is carriedout subsequent to the irradiating step (c) and is carried out by: (i)heating or microwave irradiating the second solidifiable component; (ii)irradiating the second solidifiable component with light at a wavelengthdifferent from that of the light in the irradiating step (c); (iii)contacting the second polymerizable component to water; or (iv)contacting the second polymerizable component to a catalyst.

In some embodiments, the second component comprises precursors to apolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), a silicone resin, or natural rubber, and thesolidifying and/or curing step is carried out by heating or microwaveirradiating.

In some embodiments, the second component comprises a cationically curedresin (e.g., an epoxy resin or a vinyl ether) and the solidifying and/orcuring step is carried out by irradiating the second solidifiablecomponent with light at a wavelength different from that of the light inthe irradiating step (c).

In some embodiments, the second component comprises a precursor to apolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), and the solidifying and/or curing step is carriedout by contacting the second component to water (e.g., in liquid, gas,or aerosol form). Suitable examples of such precursors include, but arenot limited to, those described in B. Baumbach, Silane TerminatedPolyurethanes (Bayer MaterialScience 2013).

In some embodiments, the second component comprises a precursor to apolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), a silicone resin, a ring-opening metathesispolymerization resin, or a click chemistry resin (alkyne monomers incombination with compound plus an azide monomers), and the solidifyingand/or curing step is carried out by contacting the second component toa polymerization catalyst (e.g., a metal catalyst such as a tincatalyst, and/or an amine catalyst, for polyurethane/polyurea resins;platinum or tin catalysts for silicone resins; ruthenium catalysts forring-opening metathesis polymerization resins; copper catalyst for clickchemistry resins; etc., which catalyst is contacted to the article as aliquid aerosol, by immersion, etc.), or an aminoplast containing resin,such as one containing N-(alkoxymethyl)acrylamide, hydroxyl groups, anda blocked acid catalyst.

In some embodiments, the irradiating step and/or advancing step iscarried out while also concurrently:

(i) continuously maintaining a dead zone (or persistent or stable liquidinterface) of polymerizable liquid in contact with the build surface,and

(ii) continuously maintaining a gradient of polymerization zone (e.g.,an active surface) between the dead zone and the solid polymer and incontact with each thereof, the gradient of polymerization zonecomprising the first component in partially cured form.

In some embodiments, the first component comprises a free radicalpolymerizable liquid and the inhibitor comprises oxygen; or the firstcomponent comprises an acid-catalyzed or cationically polymerizableliquid, and the inhibitor comprises a base.

In some embodiments, the gradient of polymerization zone and the deadzone together have a thickness of from 1 to 1000 microns.

In some embodiments, the gradient of polymerization zone is maintainedfor a time of at least 5, 10, 20 or 30 seconds, or at least 1 or 2minutes.

In some embodiments, the advancing is carried out at a cumulative rateof at least 0.1, 1, 10, 100 or 1000 microns per second.

In some embodiments, the build surface is substantially fixed orstationary in the lateral and/or vertical dimensions.

In some embodiments the method further comprises verticallyreciprocating the carrier with respect to the build surface to enhanceor speed the refilling of the build region with the polymerizableliquid.

A further aspect of the invention is a polymerizable liquidsubstantially as described herein above and below, and/or for use incarrying out a method as described herein.

In some embodiments of the methods and compositions described above andbelow, the polymerizable liquid (or “dual cure resin”) has a viscosityof 100, 200, 500 or 1,000 centipoise or more at room temperature and/orunder the operating conditions of the method, up to a viscosity of10.000, 20,000, or 50.000 centipoise or more, at room temperature and/orunder the operating conditions of the method.

One particular embodiment of the inventions disclosed herein is a methodof forming a three-dimensional object comprised of polyurethane,polyurea, or copolymer thereof, the method comprising: (a) providing acarrier and an optically transparent member having a build surface, thecarrier and the build surface defining a build region therebetween; (b)filling the build region with a polymerizable liquid, the polymerizableliquid comprising at least one of: (i) a blocked or reactive blockedprepolymer, (ii) a blocked or reactive blocked diisocyante, or (iii) ablocked or reactive blocked diisocyanate chain extender; (c) irradiatingthe build region with light through the optically transparent member toform a solid blocked polymer scaffold and advancing the carrier awayfrom the build surface to form a three-dimensional intermediate havingthe same shape as, or a shape to be imparted to, the three-dimensionalobject, with the intermediate containing the chain extender; and then(d) heating or microwave irradiating the three-dimensional intermediatesufficiently to form from the three-dimensional intermediate thethree-dimensional object comprised of polyurethane, polyurea, orcopolymer thereof.

In some embodiments, the solidifiable or polymerizable liquid is changedat least once during the method with a subsequent solidifiable orpolymerizable liquid; optionally where the subsequent solidifiable orpolymerizable liquid is cross-reactive with each previous solidifiableor polymerizable liquid during the subsequent curing, to form an objecthaving a plurality of structural segments covalently coupled to oneanother, each structural segment having different structural (e.g.,tensile) properties.

A further aspect of the inventions disclosed herein is a polymerizableliquid useful for the production of a three-dimensional object comprisedof polyurethane, polyurea, or a copolymer thereof by additivemanufacturing, the polymerizable liquid comprising a mixture of:

-   -   (a) at least one constitutent selected from the group consisting        of (i) a blocked or reactive blocked prepolymer, (ii) a blocked        or reactive blocked diisocyanate, and (iii) a blocked or        reactive blocked diisocyanate chain extender,    -   (b) optionally at least one additional chain extender.    -   (c) a photoinitiator,    -   (d) optionally a polyol and/or a polyamine,    -   (e) optionally a reactive diluent,    -   (f) optionally a non-reactive (i.e., non-reaction initiating)        light absorbing, particularly a ultraviolet light-absorbing,        pigment or dye which when present is included in an amount of        from 0.001 or 0.01 to 10 percent by weight, and    -   (g) optionally a filler (e.g., silica, a toughener such as a        core-shell rubber, etc., including combinations thereof);    -   optionally, but in some embodiments preferably, subject to the        proviso that the non-reactive light absorbing pigment or dye is        present when the at least one constituent is only the blocked or        reactive blocked prepolymer.

In some embodiments, polymerizable liquids used in the present inventioninclude a non-reactive pigment or dye. Examples include, but are notlimited to, (i) titanium dioxide (e.g., in an amount of from 0.05 or 0.1to 1 or 5 percent by weight), (ii) carbon black (e.g. included in anamount of from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) anorganic ultraviolet light absorber such as a hydroxybenzophenone,hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone,hydroxypenyltriazine, and/or benzotriazole ultraviolet light absorber(e.g., in an amount of 0.001 or 0.005 to 1, 2 or 4 percent by weight).

In some embodiments, a Lewis acid or an oxidizable tin salt is includedin the polymerizable liquid (e.g., in an amount of from 0.01 or 0.1 to 1or 2 percent by weight, or more) in an amount effective to acceleratethe formation of the three-dimensional intermediate object during theproduction thereof.

A further aspect of the inventions disclosed herein is athree-dimensional object comprised of: (a) a light polymerized firstcomponent; and (b) a second solidified component (e.g., a furtherreacted, polymerized or chain extended component) different from thefirst component; optionally but in some embodiments preferably subjectto the proviso that: (i) the second component does not contain acationic polymerization photoinitiator, and/or (ii) thethree-dimensional object is produced by the process of continuous liquidinterface production.

In some embodiments, the object further comprises: (c) a thirdsolidified (or further reacted, polymerized, or chain extended)component different from the first and second component, with the objecthaving at least a first structural segment and a second structuralsegment covalently coupled to one another, the first structural segmentcomprised of the second solidified component, the second structuralsegment comprised of the third solidified component; and both the firstand second structural segments comprised of the same or different lightpolymerized first component.

In some embodiments, the object comprises a polymer blend formed fromthe first component and the second component.

The object may be one that has a shape that cannot be formed byinjection molding or casting.

Non-limiting examples and specific embodiments of the present inventionare explained in greater detail in the drawings herein and thespecification set forth below. The disclosures of all United StatesPatent references cited herein are to be incorporated herein byreference in their entirety.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Where used, broken lines illustrate optionalfeatures or operations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “connected” to, “coupled” with, “contacting,” etc.,another element, it can be directly on, attached to, connected to,coupled with and/or contacting the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing, for example, “directly on,” “directly attached” to, “directlyconnected” to, “directly coupled” with or “directly contacting” anotherelement, there are no intervening elements present. It will also beappreciated by those of skill in the art that references to a structureor feature that is disposed “adjacent” another feature can have portionsthat overlap or underlie the adjacent feature.

Spatially relative terms, such as “under,” “below,” “lower,” “over,”“upper” and the like, may be used herein for ease of description todescribe an element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus the exemplary term “under” can encompass both anorientation of over and under. The device may otherwise be oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly,” “downwardly,” “vertical,” “horizontal” and the like are usedherein for the purpose of explanation only, unless specificallyindicated otherwise.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.Thus, a first element, component, region, layer or section discussedherein could be termed a second element, component, region, layer orsection without departing from the teachings of the present invention.The sequence of operations (or steps) is not limited to the orderpresented in the claims or figures unless specifically indicatedotherwise.

“Shape to be imparted to” refers to the case where the shape of theintermediate object slightly changes between formation thereof andforming the subsequent three-dimensional product, typically by shrinkage(e.g., up to 1, 2 or 4 percent by volume), expansion (e.g., up to 1, 2or 4 percent by volume), removal of support structures, or byintervening forming steps (e.g., intentional bending, stretching,drilling, grinding, cutting, polishing, or other intentional formingafter formation of the intermediate product, but before formation of thesubsequent three-dimensional product). As noted above, thethree-dimensional intermediate may also be washed, if desired, beforefurther curing, and/or before, during, or after any intervening formingsteps.

“Hydrocarbyl” as used herein refers to a bifunctional hydrocarbon group,which hydrocarbon may be aliphatic, aromatic, or mixed aliphatic andaromatic, and optionally containing one or more (e.g. 1, 2, 3, or 4)heteroatoms (typically selected from N, O, and S). Such hydrocarbylgroups may be optionally substituted and may contain from 1, 2, or 3carbon atoms, up to 6, 8 or 10 carbon atoms or more, and up to 40, 80,or 100 carbon atoms or more.

“Hard-segment” and “soft-segment” as used herein derive from themorphology of elastomeric polymers which can contain distinct phaseseparated regions. Such regions can be detected by thermoanalysistechniques and distinguished by, for example, glass transitiontemperatures. Generally, soft-segments of the polymer can be consideredas having glass transition temperatures below room temperature whilsthard-segments can be considered as having glass transition temperaturesabove room temperature or even melting points if a crystallite. It isthe current opinion (and hence their classification) that “soft-segment”prepolymers or resin constituents are associated with the formation ofthe soft-segment phase of the product and conversely that hard-segmentprepolymers or resin constituents are associated with the hard-segmentphase of the product. Structure-property relationships of hard- andsoft-segment phases are described for example by Redman in “Developmentsin Polyurethanes-I” J. M. Buist Ed., Elsevier, London—published 1978.See, e.g., U.S. Pat. No. 5,418,259 (Dow).

Heating may be active heating (e.g., in an oven, such as an electric,gas, or solar oven), or passive heating (e.g., at ambient temperature).Active heating will generally be more rapid than passive heating and insome embodiments is preferred, but passive heating-such as simplymaintaining the intermediate at ambient temperature for a sufficienttime to effect further cure—is in some embodiments preferred.

“Diisocyanate” and “polyisocyanate” are used interchangeably herein andrefer to aliphatic, cycloaliphatic, and aromatic isocyanates that haveat least 2, or in some embodiments more than 2, isocyanate (NCO) groupsper molecule, on average. In some embodiments, the isocyanates have, onaverage, 3 to 6, 8 or 10 or more isocyanate groups per molecule. In someembodiments, the isocvanates may be a hyperbranched or dendrimericisocyanate (e.g., containing more than 10 isocyanate groups permolecule, on average). Common examples of suitable isocyanates include,but are not limited to, methylene diphenyl diisocyanate (MDI), toluenediisocyanate (TDI)), para-phenyl diisocyanate (PPDI),4,4′-dicyclohexylmethane-diisocvanate (HMDI), hexamethylene diisocyanate(HDI), isophorone diisocyanate (IPDI),triphenylmethane-4,4′4″-triisocyanate, tolune-2,4,6-triyl triisocyanate,1,3,5-triazine-2,4,6-triisocyanate, ethyl ester L-lysine triisocyanate,etc., including combinations thereof. Numerous additional examples areknown and are described in, for example, U.S. Pat. Nos. 9,200,108;8,378,053; 7,144,955; 4,075,151, 3,932,342, and in US Patent ApplicationPublication Nos. US 20040067318 and US 20140371406, the disclosures ofall of which are incorporated by reference herein in their entirety.

Oxidizable tin salts useful for carrying out the present inventioninclude, but are not limited to, stannous butanoate, stannous octoate,stannous hexanoate, stannous heptanoate, stannous linoleate, stannousphenyl butanoate, stannous phenyl stearate, stannous phenyl oleate,stannous nonanoate, stannous decanoate, stannous undecanoate, stannousdodecanoate, stannous stearate, stannous oleate stannous undecenoate,stannous 2-ethylhexoate, dibutyl tin dilaurate, dibutyl tin dioleate,dibutyl tin distearate, dipropyl tin dilaurate, dipropyl tin dioleate,dipropyl tin distearate, dibutyl tin dihexanoate, and combinationsthereof. See also U.S. Pat. Nos. 5,298,532; 4,421,822; and 4,389,514,the disclosures of which are incorporated herein by reference. Inaddition to the foregoing oxidizable tin salts, Lewis acids such asthose described in Chu et al. in Macromolecular Symposia. Volume 95,Issue 1, pages 233-242, June 1995 are known to enhance thepolymerization rates of free-radical polymerizations and are includedherein by reference.

Any suitable filler may be used in connection with the presentinvention, depending on the properties desired in the part or object tobe made. Thus, fillers may be solid or liquid, organic or inorganic, andmay include reactive and non-reactive rubbers: siloxanes,acrylonitrile-butadiene rubbers; reactive and non-reactivethermoplastics (including but not limited to: poly(ether imides),maleimide-styrene terpolymers, polyarylates, polysulfones andpolyethersulfones, etc.) inorganic fillers such as silicates (such astalc, clays, silica, mica), glass, carbon nanotubes, graphene, cellulosenanocrystals, etc., including combinations of all of the foregoing.Suitable fillers include tougheners, such as core-shell rubbers, asdiscussed below.

Tougheners.

One or more polymeric and/or inorganic tougheners can be used as afiller in the present invention. See generally US Patent ApplicationPublication No. 20150215430. The toughener may be uniformly distributedin the form of particles in the cured product. The particles could beless than 5 microns (um) in diameter. Such tougheners include, but arenot limited to, those formed from elastomers, branched polymers,hyperbranched polymers, dendrimers, rubbery polymers, rubberycopolymers, block copolymers, core-shell particles, oxides or inorganicmaterials such as clay, polyhedral oligomeric silsesquioxanes (POSS),carbonaceous materials (e.g., carbon black, carbon nanotubes, carbonnanofibers, fullerenes), ceramics and silicon carbides, with or withoutsurface modification or functionalization. Examples of block copolymersinclude the copolymers whose composition is described in U.S. Pat. No.6,894,113 (Court et al., Atofina, 2005) and include “NANOSTRENTH®™” SBM(polystyrene-polybutadiene-polymethacrylate), and AMA(polymethacrylate-polybutylacrylate-polymethacrylate), both produced byArkema. Other suitable block copolymers include FORTEGRA®™ and theamphiphilic block copolymers described in U.S. Pat. No. 7,820,760B2,assigned to Dow Chemical. Examples of known core-shell particles includethe core-shell (dendrimer) particles whose compositions are described inUS20100280151A1 (Nguyen et al., Toray Industries. Inc., 2010) for anamine branched polymer as a shell grafted to a core polymer polymerizedfrom polymerizable monomers containing unsaturated carbon-carbon bonds,core-shell rubber particles whose compositions are described in EP1632533A1 and EP 2123711A1 by Kaneka Corporation, and the “KaneAce MX”product line of such particle/epoxy blends whose particles have apolymeric core polymerized from polymerizable monomers such asbutadiene, styrene, other unsaturated carbon-carbon bond monomer, ortheir combinations, and a polymeric shell compatible with the epoxy,typically polymethylmethacrylate, polyglycidylmethacrylate,polyacrylonitrile or similar polymers, as discussed further below. Alsosuitable as block copolymers in the present invention are the “JSR SX”series of carboxylated polystyrene/polydivinylbenzenes produced by JSRCorporation; “Kureha Paraloid” EXL-2655 (produced by Kureha ChemicalIndustry Co., Ltd.), which is a butadiene alkyl methacrylate styrenecopolymer; “Stafiloid” AC-3355 and TR-2122 (both produced by TakedaChemical Industries, Ltd.), each of which are acrylate methacrylatecopolymers; and “PARALOID” EXL-2611 and EXL-3387 (both produced by Rohm& Haas), each of which are butyl acrylate methyl methacrylatecopolymers. Examples of suitable oxide particles include NANOPOX®™produced by nanoresins AG. This is a master blend of functionalizednanosilica particles and an epoxy.

Core-Shell Rubbers.

Core-shell rubbers are particulate materials (particles) having arubbery core. Such materials are known and described in, for example, USPatent Application Publication No. 20150184039, as well as US PatentApplication Publication No. 20150240113, and U.S. Pat. Nos. 6,861,475,7,625,977, 7,642,316, 8,088,245, and elsewhere.

In some embodiments, the core-shell rubber particles are nanoparticles(i.e., having an average particle size of less than 1000 nanometers(nm)). Generally, the average particle size of the core-shell rubbernanoparticles is less than 500 nm. e.g., less than 300 nm, less than 200nm, less than 100 nm, or even less than 50 nm. Typically, such particlesare spherical, so the particle size is the diameter; however, if theparticles are not spherical, the particle size is defined as the longestdimension of the particle.

In some embodiments, the rubbery core can have a Tg of less than −25°C., more preferably less than −50° C., and even more preferably lessthan −70° C. The Tg of the rubbery core may be well below −100° C. Thecore-shell rubber also has at least one shell portion that preferablyhas a Tg of at least 50° C. By “core,” it is meant an internal portionof the core-shell rubber. The core may form the center of the core-shellparticle, or an internal shell or domain of the core-shell rubber. Ashell is a portion of the core-shell rubber that is exterior to therubbery core. The shell portion (or portions) typically forms theoutermost portion of the core-shell rubber particle. The shell materialcan be grafted onto the core or is cross-linked. The rubbery core mayconstitute from 50 to 95%, or from 60 to 90%, of the weight of thecore-shell rubber particle.

The core of the core-shell rubber may be a polymer or copolymer of aconjugated diene such as butadiene, or a lower alkyl acrylate such asn-butyl-, ethyl-, isobutyl- or 2-ethylhexylacrylate. The core polymermay in addition contain up to 20% by weight of other copolymerizedmono-unsaturated monomers such as styrene, vinyl acetate, vinylchloride, methyl methacrylate, and the like. The core polymer isoptionally cross-linked. The core polymer optionally contains up to 5%of a copolymerized graft-linking monomer having two or more sites ofunsaturation of unequal reactivity, such as diallyl maleate, monoallylfumarate, allyl methacrylate, and the like, at least one of the reactivesites being non-conjugated.

The core polymer may also be a silicone rubber. These materials oftenhave glass transition temperatures below −100° C. Core-shell rubbershaving a silicone rubber core include those commercially available fromWacker Chemie, Munich, Germany, under the trade name Genioperl.

The shell polymer, which is optionally chemically grafted orcross-linked to the rubber core, can be polymerized from at least onelower alkyl methacrylate such as methyl methacrylate, ethyl methacrylateor t-butyl methacrylate. Homopolymers of such methacrylate monomers canbe used. Further, up to 40% by weight of the shell polymer can be formedfrom other monovinylidene monomers such as styrene, vinyl acetate, vinylchloride, methyl acrylate, ethyl acrylate, butyl acrylate, and the like.The molecular weight of the grafted shell polymer can be between 20,000and 500,000.

One suitable type of core-shell rubber has reactive groups in the shellpolymer which can react with an epoxy resin or an epoxy resin hardener.Glycidyl groups are suitable. These can be provided by monomers such asglycidyl methacrylate.

One example of a suitable core-shell rubber is of the type described inUS Patent Application Publication No. 2007/0027233 (EP 1 632 533 A1).Core-shell rubber particles as described therein include a cross-linkedrubber core, in most cases being a cross-linked copolymer of butadiene,and a shell which is preferably a copolymer of styrene, methylmethacrylate, glycidyl methacrylate and optionally acrylonitrile. Thecore-shell rubber is preferably dispersed in a polymer or an epoxyresin, also as described in the document.

Suitable core-shell rubbers include, but are not limited to, those soldby Kaneka Corporation under the designation Kaneka Kane Ace, includingthe Kaneka Kane Ace 15 and 120 series of products, including KanakaKance Ace MX 120, Kaneka Kane Ace MX 153, Kaneka Kane Ace MX 154, KanekaKane Ace MX 156, Kaneka Kane Ace MX170, and Kaneka Kane Ace MX 257 andKaneka Kane Ace MX 120 core-shell rubber dispersions, and mixturesthereof.

I. Polymerizable Liquids: Part A.

Dual cure systems as described herein may include a first curable system(sometimes referred to as “Part A” or herein) that is curable by actinicradiation, typically light, and in some embodiments ultraviolet (UV)light). Any suitable polymerizable liquid can be used as the firstcomponent. The liquid (sometimes also referred to as “liquid resin”“ink,” or simply “resin” herein) can include a monomer, particularlyphotopolymerizable and/or free radical polymerizable monomers, and asuitable initiator such as a free radical initiator, and combinationsthereof. Examples include, but are not limited to, acrylics,methacrylics, acrylamides, styrenics, olefins, halogenated olefins,cyclic alkenes, maleic anhydride, alkenes, alkynes, carbon monoxide,functionalized oligomers, multifunctional cute site monomers,functionalized PEGs, etc., including combinations thereof. Examples ofliquid resins, monomers and initiators include but are not limited tothose set forth in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476;7,767,728; 7,649,029; WO 2012129968 A1; CN 102715751 A; JP 2012210408 A.

Acid Catalyzed Polymerizable Liquids.

While in some embodiments as noted above the polymerizable liquidcomprises a free radical polymerizable liquid (in which case aninhibitor may be oxygen as described below), in other embodiments thepolymerizable liquid comprises an acid catalyzed, or cationicallypolymerized, polymerizable liquid. In such embodiments the polymerizableliquid comprises monomers contain groups suitable for acid catalysis,such as epoxide groups, vinyl ether groups, etc. Thus suitable monomersinclude olefins such as methoxyethene, 4-methoxystyrene, styrene,2-methylprop-1-ene, 1,3-butadiene, etc.; heterocycloic monomers(including lactones, lactams, and cyclic amines) such as oxirane,thietane, tetrahydrofuran, oxazoline, 1,3, dioxepane, oxetan-2-one,etc., and combinations thereof. A suitable (generally ionic ornon-ionic) photoacid generator (PAG) is included in the acid catalyzedpolymerizable liquid, examples of which include, but are not limited toonium salts, sulfonium and iodonium salts, etc., such as diphenyl iodidehexafluorophosphate, diphenyl iodide hexafluoroarsenate, diphenyl iodidehexafluoroantimonate, diphenyl p-methoxyphenyl triflate, diphenylp-toluenyl triflate, diphenyl p-isobutylphenyl triflate, diphenylp-tert-butylphenyl triflate, triphenylsulfonium hexafluororphosphate,triphenylsulfonium hexafluoroarsenate, triphenylsulfoniumhexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, etc., including mixtures thereof.See. e.g., U.S. Pat. Nos. 7,824,839; 7,550,246; 7,534,844; 6,692,891;5,374,500; and 5,017,461; see also Photoacid Generator Selection Guidefor the Electronics Industry and Energy Curable Coatings (BASF 2010).

Hydrogels.

In some embodiments suitable resins includes photocurable hydrogels likepoly(ethylene glycols) (PEG) and gelatins. PEG hydrogels have been usedto deliver a variety of biologicals, including Growth factors; however,a great challenge facing PEG hydrogels crosslinked by chain growthpolymerizations is the potential for irreversible protein damage.Conditions to maximize release of the biologicals from photopolymerizedPEG diacrylate hydrogels can be enhanced by inclusion of affinitybinding peptide sequences in the monomer resin solutions, prior tophotopolymerization allowing sustained delivery. Gelatin is a biopolymerfrequently used in food, cosmetic, pharmaceutical and photographicindustries. It is obtained by thermal denaturation or chemical andphysical degradation of collagen. There are three kinds of gelatin,including those found in animals, fish and humans. Gelatin from the skinof cold water fish is considered safe to use in pharmaceuticalapplications. UV or visible light can be used to crosslink appropriatelymodified gelatin. Methods for crosslinking gelatin include curederivatives from dyes such as Rose Bengal.

Photocurable Silicone Resins.

A suitable resin includes photocurable silicones. UV cure siliconerubber, such as Siliopren™ UV Cure Silicone Rubber can be used as canLOCTITE™ Cure Silicone adhesives sealants. Applications include opticalinstruments, medical and surgical equipment, exterior lighting andenclosures, electrical connectors/sensors, fiber optics, gaskets, andmolds.

Biodegradable Resins.

Biodegradable resins are particularly important for implantable devicesto deliver drugs or for temporary performance applications, likebiodegradable screws and stents (U.S. Pat. Nos. 7,919,162; 6,932,930).Biodegradable copolymers of lactic acid and glycolic acid (PLGA) can bedissolved in PEG di(meth)acrylate to yield a transparent resin suitablefor use. Polycaprolactone and PLGA oligomers can be functionalized withacrylic or methacrylic groups to allow them to be effective resins foruse.

Photocurable Polyurethanes.

A particularly useful resin is photocurable polyurethanes (including,polyureas, and copolymers of polyurethanes and polyureas (e.g.,poly(urethane-urea)). A photopolymerizable polyurethane/polyureacomposition comprising (1) a polyurethane based on an aliphaticdiisocyanate, poly(hexamethylene isophthalate glycol) and, optionally,1,4-butanediol; (2) a polyfunctional acrylic ester; (3) aphotoinitiator; and (4) an anti-oxidant, can be formulated so that itprovides a hard, abrasion-resistant, and stain-resistant material (U.S.Pat. No. 4,337,130). Photocurable thermoplastic polyurethane elastomersincorporate photoreactive diacetylene diols as chain extenders.

High Performance Resins.

In some embodiments, high performance resins are used. Such highperformance resins may sometimes require the use of heating to meltand/or reduce the viscosity thereof, as noted above and discussedfurther below. Examples of such resins include, but are not limited to,resins for those materials sometimes referred to as liquid crystallinepolymers of esters, ester-imide, and ester-amide oligomers, as describedin U.S. Pat. Nos. 7,507,784; 6,939,940. Since such resins are sometimesemployed as high-temperature thermoset resins, in the present inventionthey further comprise a suitable photoinitiator such as benzophenone,anthraquinone, amd fluoroenone initiators (including derivativesthereof), to initiate cross-linking on irradiation, as discussed furtherbelow.

Additional Example Resins.

Particularly useful resins for dental applications include EnvisionTEC'sClear Guide, EnvisionTEC's E-Denstone Material. Particularly usefulresins for hearing aid industries include EnvisionTEC's e-Shell 300Series of resins. Particularly useful resins include EnvisionTEC'sHTM140IV High Temperature Mold Material for use directly with vulcanizedrubber in molding/casting applications. A particularly useful materialfor making tough and stiff parts includes EnvisionTEC's RC31 resin.Particularly useful resin for investment casting applications includeEnvisionTEC's Easy Cast EC500 resin and MadeSolid FireCast resin.

Additional Resin Ingredients.

The liquid resin or polymerizable material can have solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. The particles can bemetallic, organic/polymeric, inorganic, or composites or mixturesthereof. The particles can be nonconductive, semi-conductive, orconductive (including metallic and non-metallic or polymer conductors);and the particles can be magnetic, ferromagnetic, paramagnetic, ornonmagnetic. The particles can be of any suitable shape, includingspherical, elliptical, cylindrical, etc. The particles can be of anysuitable size (for example, ranging from 1 nm to 20 um averagediameter).

The particles can comprise an active agent or detectable compound asdescribed below, though these may also be provided dissolved solubilizedin the liquid resin as also discussed below. For example, magnetic orparamagnetic particles or nanoparticles can be employed.

The liquid resin can have additional ingredients solubilized therein,including pigments, dyes, active compounds or pharmaceutical compounds,detectable compounds (e.g., fluorescent, phosphorescent, radioactive),etc., again depending upon the particular purpose of the product beingfabricated. Examples of such additional ingredients include, but are notlimited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA,sugars, small organic compounds (drugs and drug-like compounds), etc.,including combinations thereof.

Non-Reactive Light Absorbers.

In some embodiments, polymerizable liquids for carrying out the presentinvention include a non-reactive pigment or dye that absorbs light,particularly UV light. Suitable examples of such light absorbersinclude, but are not limited to: (i) titanium dioxide (e.g., included inan amount of from 0.05 or 0.1 to 1 or 5 percent by weight), (ii) carbonblack (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percentby weight), and/or (iii) an organic ultraviolet light absorber such as ahydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide,benzophenone, thioxanthone, hydroxypenyltriazine, and/or benzotriazoleultraviolet light absorber (e.g., Mayzo BLS 1326) (e.g., included in anamount of 0.001 or 0.005 to 1, 2 or 4 percent by weight). Examples ofsuitable organic ultraviolet light absorbers include, but are notlimited to, those described in U.S. Pat. Nos. 3,213,058; 6,916,867;7,157,586; and 7,695, 643, the disclosures of which are incorporatedherein by reference.

Inhibitors of Polymerization.

Inhibitors or polymerization inhibitors for use in the present inventionmay be in the form of a liquid or a gas. In some embodiments, gasinhibitors are preferred. In some embodiments, liquid inhibitors such asoils or lubricants (e.g., fluorinated oils such as perfluoropolyethers)may be employed, as inhibitors (or as release layers that maintain aliquid interface)). The specific inhibitor will depend upon the monomerbeing polymerized and the polymerization reaction. For free radicalpolymerization monomers, the inhibitor can conveniently be oxygen, whichcan be provided in the form of a gas such as air, a gas enriched inoxygen (optionally but in some embodiments preferably containingadditional inert gases to reduce combustibility thereof), or in someembodiments pure oxygen gas. In alternate embodiments, such as where themonomer is polymerized by photoacid generator initiator, the inhibitorcan be a base such as ammonia, trace amines (e.g. methyl amine, ethylamine, di and trialkyl amines such as dimethyl amine, diethyl amine,trimethyl amine, triethyl amine, etc.), or carbon dioxide, includingmixtures or combinations thereof.

Polymerizable Liquids Carrying Live Cells.

In some embodiments, the polymerizable liquid may carry live cells as“particles” therein. Such polymerizable liquids are generally aqueous,and may be oxygenated, and may be considered as “emulsions” where thelive cells are the discrete phase. Suitable live cells may be plantcells (e.g., monocot, dicot), animal cells (e.g., mammalian, avian,amphibian, reptile cells), microbial cells (e.g., prokaryote, eukaryote,protozoal, etc.), etc. The cells may be of differentiated cells from orcorresponding to any type of tissue (e.g., blood, cartilage, bone,muscle, endocrine gland, exocrine gland, epithelial, endothelial, etc.),or may be undifferentiated cells such as stem cells or progenitor cells.In such embodiments the polymerizable liquid can be one that forms ahydrogel, including but not limited to those described in U.S. Pat. Nos.7,651,683; 7,651,682; 7,556,490; 6,602,975; 5,836,313; etc.

II. Methods and Apparatus.

The three-dimensional intermediate is preferably formed from resins asdescribed above by additive manufacturing, typically bottom-up ortop-down additive manufacturing, generally known as stereolithography.Such methods are known and described in, for example, U.S. Pat. No.5,236,637 to Hull, U.S. Pat. Nos. 5,391,072 and 5,529,473 to Lawton,U.S. Pat. No. 7,438,846 to John, U.S. Pat. No. 7,892,474 to Shkolnik,U.S. Pat. No. 8,110,135 to El-Siblani, U.S. Patent ApplicationPublication Nos. 2013/0292862 to Joyce, and US Patent ApplicationPublication No. 2013/0295212 to Chen et al. The disclosures of thesepatents and applications are incorporated by reference herein in theirentirety.

In general, top-down three-dimensional fabrication is carried out by:

(a) providing a polymerizable liquid reservoir having a polymerizableliquid fill level and a carrier positioned in the reservoir, the carrierand the fill level defining a build region therebetween:

(b) filling the build region with a polymerizable liquid (i.e., theresin), said polymerizable liquid comprising a mixture of (i) a light(typically ultraviolet light) polymerizable liquid first component, and(ii) a second solidifiable component of the dual cure system; and then

(c) irradiating the build region with light to form a solid polymerscaffold from the first component and also advancing (typicallylowering) the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object and containing said secondsolidifiable component (e.g., a second reactive component) carried inthe scaffold in unsolidified and/or uncured form.

A wiper blade, doctor blade, or optically transparent (rigid orflexible) window, may optionally be provided at the fill level tofacilitate leveling of the polymerizable liquid, in accordance withknown techniques. In the case of an optically transparent window, thewindow provides a build surface against which the three-dimensionalintermediate is formed, analogous to the build surface in bottom-upthree-dimensional fabrication as discussed below.

In general, bottom-up three-dimensional fabrication is carried out by:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween:

(b) filling the build region with a polymerizable liquid (i.e., theresin), said polymerizable liquid comprising a mixture of (i) a light(typically ultraviolet light) polymerizable liquid first component, and(ii) a second solidifiable component of the dual cure system; and then

(c) irradiating the build region with light through said opticallytransparent member to form a solid polymer scaffold from the firstcomponent and also advancing (typically raising) the carrier away fromthe build surface to form a three-dimensional intermediate having thesame shape as, or a shape to be imparted to, the three-dimensionalobject and containing said second solidifiable component (e.g., a secondreactive component) carried in the scaffold in unsolidified and/oruncured form.

In some embodiments of bottom-up or top-down three-dimensionalfabrication as implemented in the context of the present invention, thebuild surface is stationary during the formation of thethree-dimensional intermediate; in other embodiments of bottom-upthree-dimensional fabrication as implemented in the context of thepresent invention, the build surface is tilted, slid, flexed and/orpeeled, and/or otherwise translocated or released from the growingthree-dimensional intermediate, usually repeatedly, during formation ofthe three-dimensional intermediate.

In some embodiments of bottom-up or top-down three-dimensionalfabrication as carried out in the context of the present invention, thepolymerizable liquid (or resin) is maintained in liquid contact withboth the growing three dimensional intermediate and the build surfaceduring both the filling and irradiating steps, during fabrication ofsome of, a major portion of, or all of the three-dimensionalintermediate.

In some embodiments of bottom-up or top down three-dimensionalfabrication as carried out in the context of the present invention, thegrowing three-dimensional intermediate is fabricated in a layerlessmanner (e.g., through multiple exposures or “slices” of patternedactinic radiation or light) during at least a portion of the formationof the three-dimensional intermediate.

In some embodiments of bottom up or top down three-dimensionalfabrication as carried out in the context of the present invention, thegrowing three-dimensional intermediate is fabricated in a layer-by-layermanner (e.g., through multiple exposures or “slices” of patternedactinic radiation or light), during at least a portion of the formationof the three-dimensional intermediate.

In some embodiments of bottom-up or top-down three-dimensionalfabrication employing a rigid or flexible optically transparent window,a lubricant or immiscible liquid may be provided between the window andthe polymerizable liquid (e.g., a fluorinated fluid or oil such as aperfluoropolyether oil).

From the foregoing it will be appreciated that, in some embodiments ofbottom-up or top down three-dimensional fabrication as carried out inthe context of the present invention, the growing three-dimensionalintermediate is fabricated in a layerless manner during the formation ofat least one portion thereof, and that same growing three-dimensionalintermediate is fabricated in a layer-by-layer manner during theformation of at least one other portion thereof. Thus, operating modemay be changed once, or on multiple occasions, between layerlessfabrication and layer-by-layer fabrication, as desired by operatingconditions such as part geometry.

In some embodiments, the intermediate is formed by continuous liquidinterface production (CLIP). CLIP is known and described in, forexample, PCT Applications Nos. PCT/US2014/015486 (published as U.S. Pat.No. 9,211,678 on Dec. 15, 2015); PCT/US2014/015506 (also published asU.S. Pat. No. 9,205,601 on Dec. 8, 2015), PCT/US2014/015497 (alsopublished as U.S. Pat. No. 9,216,546 on Dec. 22, 2015), and in J.Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquidinterface production of 3D Objects, Science 347, 1349-1352 (publishedonline 16 Mar. 2015). See also R. Janusziewcz et al., Layerlessfabrication with continuous liquid interface production, Proc. Natl.Acad. Sci. USA 113, 11703-11708 (Oct. 18, 2016). In some embodiments,CLIP employs features of a bottom-up three-dimensional fabrication asdescribed above, but the irradiating and/or said advancing steps arecarried out while also concurrently maintaining a stable or persistentliquid interface between the growing object and the build surface orwindow, such as by: (i) continuously maintaining a dead zone ofpolymerizable liquid in contact with said build surface, and (ii)continuously maintaining a gradient of polymerization zone (such as anactive surface) between the dead zone and the solid polymer and incontact with each thereof, the gradient of polymerization zonecomprising the first component in partially cured form. In someembodiments of CLIP, the optically transparent member comprises asemipermeable member (e.g., a fluoropolymer), and the continuouslymaintaining a dead zone is carried out by feeding an inhibitor ofpolymerization through the optically transparent member, therebycreating a gradient of inhibitor in the dead zone and optionally in atleast a portion of the gradient of polymerization zone. Other approachesfor carrying out CLIP that can be used in the present invention andpotentially obviate the need for a semipermeable “window” or windowstructure include utilizing a liquid interface comprising an immiscibleliquid (see L. Robeson et al., WO 2015/164234, published Oct. 29, 2015),generating oxygen as an inhibitor by electrolysis (see 1 Craven et al.,WO 2016/133759, published Aug. 25, 2016), and incorporating magneticallypositionable particles to which the photoactivator is coupled into thepolymerizable liquid (see J. Rolland, WO 2016/145182, published Sep. 15,2016).

As noted above, the present invention provides (in some embodiments) amethod of forming a three-dimensional object, comprising the steps of:(a) providing a carrier and a build plate, the build plate comprising asemipermeable member, the semipermeable member comprising a buildsurface and a feed surface separate from the build surface, with thebuild surface and the carrier defining a build region therebetween, andwith the feed surface in fluid contact with a polymerization inhibitor;then (concurrently and/or sequentially) (b) filing the build region witha polymerizable liquid, the polymerizable liquid contacting the buildsegment, (c) irradiating the build region through the build plate toproduce a solid polymerized region in the build region, with a liquidfilm release layer comprised of the polymerizable liquid formed betweenthe solid polymerized region and the build surface, the polymerizationof which liquid film is inhibited by the polymerization inhibitor; and(d) advancing the carrier with the polymerized region adhered theretoaway from the build surface on the stationary build plate to create asubsequent build region between the polymerized region and the top zone.In general the method includes (e) continuing and/or repeating steps (b)through (d) to produce a subsequent polymerized region adhered to aprevious polymerized region until the continued or repeated depositionof polymerized regions adhered to one another forms thethree-dimensional object.

Since no mechanical release of a release layer is required, or nomechanical movement of a build surface to replenish oxygen or otherinhibitor is required, the method can be carried out in a continuousfashion, though it will be appreciated that the individual steps notedabove may be carried out sequentially, concurrently, or a combinationthereof. Indeed, the rate of steps can be varied over time dependingupon factors such as the density and/or complexity of the region underfabrication.

Also, since mechanical release from a window or from a release layergenerally requires that the carrier be advanced a greater distance fromthe build plate than desired for the next irradiation step, whichenables the window to be recoated, and then return of the carrier backcloser to the build plate (e.g., a “two steps forward one step back”operation), the present invention in some embodiments permitselimination of this “back-up” step and allows the carrier to be advancedunidirectionally, or in a single direction, without intervening movementof the window for re-coating, or “snapping” of a pre-formed elasticrelease-layer. However, in other embodiments of the invention,reciprocation is utilized not for the purpose of obtaining release, butfor the purpose of more rapidly filling or pumping polymerizable liquidinto the build region.

While the dead zone and the gradient of polymerization zone do not havea strict boundary therebetween (in those locations where the two meet),the thickness of the gradient of polymerization zone is in someembodiments at least as great as the thickness of the dead zone. Thus,in some embodiments, the dead zone has a thickness of from 0.01, 0.1, 1,2, or 10 microns up to 100, 200 or 400 microns, or more, and/or thegradient of polymerization zone and the dead zone together have athickness of from 1 or 2 microns up to 400, 600, or 1000 microns, ormore. Thus the gradient of polymerization zone may be thick or thindepending on the particular process conditions at that time. Where thegradient of polymerization zone is thin, it may also be described as anactive surface on the bottom of the growing three-dimensional object,with which monomers can react and continue to form growing polymerchains therewith. In some embodiments, the gradient of polymerizationzone, or active surface, is maintained (while polymerizing stepscontinue) for a time of at least 5, 10, 15, 20 or 30 seconds, up to 5,10, 15 or 20 minutes or more, or until completion of thethree-dimensional product.

The method may further comprise the step of disrupting the gradient ofpolymerization zone for a time sufficient to form a cleavage line in thethree-dimensional object (e.g., at a predetermined desired location forintentional cleavage, or at a location in the object where prevention ofcleavage or reduction of cleavage is non-critical), and then reinstatingthe gradient of polymerization zone (e.g. by pausing, and resuming, theadvancing step, increasing, then decreasing, the intensity ofirradiation, and combinations thereof).

In some embodiments, the advancing step is carried out sequentially inuniform increments (e.g., of from 0.1 or 1 microns, up to 10 or 100microns, or more) for each step or increment. In some embodiments, theadvancing step is carried out sequentially in variable increments (e.g.,each increment ranging from 0.1 or 1 microns, up to 10 or 100 microns,or more) for each step or increment. The size of the increment, alongwith the rate of advancing, will depend in part upon factors such astemperature, pressure, structure of the article being produced (e.g.,size, density, complexity, configuration, etc.)

In other embodiments of the invention, the advancing step is carried outcontinuously, at a uniform or variable rate.

In some embodiments, the rate of advance (whether carried outsequentially or continuously) is from about 0.1 l, or 10 microns persecond, up to about to 100, 1,000, or 10,000 microns per second, againdepending again depending on factors such as temperature, pressure,structure of the article being produced, intensity of radiation, etc

As described further below, in some embodiments the filling step iscarried out by forcing the polymerizable liquid into the build regionunder pressure. In such a case, the advancing step or steps may becarried out at a rate or cumulative or average rate of at least 0.1, 1,10, 50, 100, 500 or 1000 microns per second, or more. In general, thepressure may be whatever is sufficient to increase the rate of theadvancing step(s) at least 2, 4, 6, 8 or 10 times as compared to themaximum rate of repetition of the advancing steps in the absence of thepressure. Where the pressure is provided by enclosing an apparatus suchas described above in a pressure vessel and carrying the process out ina pressurized atmosphere (e.g., of air, air enriched with oxygen, ablend of gasses, pure oxygen, etc.) a pressure of 10, 20, 30 or 40pounds per square inch (PSI) up to, 200, 300), 400 or 500 PSI or more,may be used. For fabrication of large irregular objects higher pressuresmay be less preferred as compared to slower fabrication times due to thecost of a large high pressure vessel. In such an embodiment, both thefeed surface and the polymerizable liquid can be are in fluid contactwith the same compressed gas (e.g., one comprising from 20 to 95 percentby volume of oxygen, the oxygen serving as the polymerization inhibitor.

On the other hand, when smaller items are fabricated, or a rod or fiberis fabricated that can be removed or exited from the pressure vessel asit is produced through a port or orifice therein, then the size of thepressure vessel can be kept smaller relative to the size of the productbeing fabricated and higher pressures can (if desired) be more readilyutilized.

As noted above, the irradiating step is in some embodiments carried outwith patterned irradiation. The patterned irradiation may be a fixedpattern or may be a variable pattern created by a pattern generator(e.g., a DLP) as discussed above, depending upon the particular itembeing fabricated.

When the patterned irradiation is a variable pattern rather than apattern that is held constant over time, then each irradiating step maybe any suitable time or duration depending on factors such as theintensity of the irradiation, the presence or absence of dyes in thepolymerizable material, the rate of growth, etc. Thus in someembodiments each irradiating step can be from 0.001, 0.01, 0.1, 1 or 10microseconds, up to 1, 10, or 100 minutes, or more, in duration. Theinterval between each irradiating step is in some embodiments preferablyas brief as possible, e.g., from 0.001, 0.01, 0.1, or 1 microseconds upto 0.1, 1, or 10 seconds. In example embodiments, the pattern may varyhundreds, thousands or millions of times to impart shape changes on thethree-dimensional object being formed. In addition, in exampleembodiments, the pattern generator may have high resolution withmillions of pixel elements that can be varied to change the shape thatis imparted. For example, the pattern generator may be a DLP with morethan 1,000 or 2,000 or 3,000 or more rows and/or more than 1,000 or2,000 or 3,000 or more columns of micromirrors, or pixels in a liquidcrystal display panel, that can be used to vary the shape. In exampleembodiments, the three-dimensional object may be formed through thegradient of polymerization allowing the shape changes to be impartedwhile continuously printing. In example embodiments, this allows complexthree-dimensional objects to be formed at high speed with asubstantially continuous surface without cleavage lines or seams. Insome examples, thousands or millions of shape variations may be impartedon the three-dimensional object being formed without cleavage lines orseams across a length of the object being formed of more than 1 mm, 1cm, 10 cm or more or across the entire length of the formed object. Inexample embodiments, the object may be continuously formed through thegradient of polymerization at a rate of more than 1, 10, 100, 1000,10000 or more microns per second.

In some embodiments the build surface is flat; in other the buildsurface is irregular such as convexly or concavely curved, or has wallsor trenches formed therein. In either case the build surface may besmooth or textured.

Curved and/or irregular build plates or build surfaces can be used infiber or rod formation, to provide different materials to a singleobject being fabricated (that is, different polymerizable liquids to thesame build surface through channels or trenches formed in the buildsurface, each associated with a separate liquid supply, etc.

III. Dual Hardening Polymerizable Liquids: Part B.

Dual cure stereolithography resins suitable for stereolithographytechniques (particularly for CLIP) are described in J. Rolland et al.,PCT Applications PCT/US2015/036893 (see also US Patent Application Pub.No. US 2016/0136889), PCT/US2015/036902 (see also US Patent ApplicationPub. No. US 2016/0137838), PCT/US2015/036924 (see also US PatentApplication Pub. No. US 2016/016077), and PCT/US2015/036946 (see alsoU.S. Pat. No. 9,453,142). These resins usually include a firstpolymerizable system typically polymerized by light (sometimes referredto as “Part A”) from which an intermediate object is produced, and alsoinclude at least a second polymerizable system (“Part B”) which isusually cured after the intermediate object is first formed, and whichimpart desirable structural and/or tensile properties to the finalobject.

As noted above, in some embodiments of the invention, the polymerizableliquid comprises a first light polymerizable component (sometimesreferred to as “Part A” herein) and a second component that solidifiesby another mechanism, or in a different manner from, the first component(sometimes referred to as “Part B” herein), typically by furtherreacting, polymerizing, or chain extending. Numerous embodiments thereofmay be carried out. In the following, note that, where particularacrylates such as methacrylates are described, other acrylates may alsobe used.

Part A Chemistry.

As noted above, in some embodiments of the present invention, a resinwill have a first component, termed “Part A.” Part A comprises orconsists of a mix of monomers and/or prepolymers that can be polymerizedby exposure to actinic radiation or light. This resin can have afunctionality of 2 or higher (though a resin with a functionality of 1can also be used when the polymer does not dissolve in its monomer). Apurpose of Part A is to “lock” the shape of the object being formed orcreate a scaffold for the one or more additional components (e.g., PartB). Importantly, Part A is present at or above the minimum quantityneeded to maintain the shape of the object being formed after theinitial solidification. In some embodiments, this amount corresponds toless than ten, twenty, or thirty percent by weight of the total resin(polymerizable liquid) composition.

In some embodiments, Part A can react to form a cross-linked polymernetwork or a solid homopolymer.

Examples of suitable reactive end groups suitable for Part Aconstituents, monomers, or prepolymers include, but are not limited to:acrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

An aspect of the solidification of Part A is that it provides a scaffoldin which a second reactive resin component, termed “Part B,” cansolidify during a second step (which may occur concurrently with orfollowing the solidification of Part A). This secondary reactionpreferably occurs without significantly distorting the original shapedefined during the solidification of Part A. Alternative approacheswould lead to a distortion in the original shape in a desired manner.

In particular embodiments, when used in the methods and apparatusdescribed herein, the solidification of Part A is continuously inhibitedduring printing within a certain region, by oxygen or amines or otherreactive species, to form a liquid interface between the solidified partand an inhibitor-permeable film or window (e.g., is carried out bycontinuous liquid interphase/interface printing).

Part B Chemistry.

Part B may comprise, consist of or consist essentially of a mix ofmonomers and/or prepolymers that possess reactive end groups thatparticipate in a second solidification reaction after the Part Asolidification reaction. In some embodiments, Part B could be addedsimultaneously to Part A so it is present during the exposure toactinide radiation, or Part B could be infused into the object madeduring the 3D printing process in a subsequent step. Examples of methodsused to solidify Part B include, but are not limited to, contacting theobject or scaffold to heat, water or water vapor, light at a differentwavelength than that at which Part A is cured, catalysts, (with orwithout additional heat), evaporation of a solvent from thepolymerizable liquid (e.g., using heat, vacuum, or a combinationthereof), microwave irradiation, etc., including combinations thereof.

Examples of suitable reactive end group pairs suitable for Part Bconstituents, monomers or prepolymers include, but are not limited to:epoxy/amine, epoxy/hydroxyl, oxetane/amine, oxetane/alcohol,isocyanate/hydroxyl, Isocyanate/amine, isocyanate/carboxylic acid,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H(hydrosilylation), Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde,amine/aldehyde, hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast,alkyne/Azide (also known as one embodiment of “Click Chemistry,” alongwith additional reactions including thiolene, Michael additions,Diels-Alder reactions, nucleophilic substitution reactions, etc.),alkene/Sulfur (polybutadiene vulcanization), alkene/peroxide,alkene/thiol, alkyne/thiol, hydroxyl/halide, isocyanate*/water(polyurethane foams), Si—OH/hydroxyl, Si—OH/water, Si—OH/Si—H (tincatalyzed silicone), Si—OH/Si—OH (tin catalyzed silicone),Perfluorovinyl (coupling to form perfluorocyclobutane), etc., where*Isocyanates include protected isocyanates (e.g. oximes)),diene/dienophiles for Diels-Alder reactions, olefin metathesispolymerization, olefin polymerization using Ziegler-Natta catalysis,ring-opening polymerization (including ring-opening olefin metathesispolymerization, lactams, lactones, Siloxanes, epoxides, cyclic ethers,imines, cyclic acetals, etc.), etc.

Other reactive chemistries suitable for Part B will be recognizable bythose skilled in the art. Part B components useful for the formation ofpolymers described in “Concise Polymeric Materials Encyclopedia” and the“Encyclopedia of Polymer Science and Technology” are hereby incorporatedby reference.

Organic Peroxides.

In some embodiments, an organic peroxide may be included in thepolymerizable liquid or resin, for example to facilitate the reaction ofpotentially unreacted double bonds during heat and/or microwaveirradiation curing. Such organic peroxides may be included in the resinor polymerizable liquid in any suitable amount, such as from 0.001 or0.01 or 0.1 percent by weight, up to 1, 2, or 3 percent by weight.Examples of suitable organic peroxides include, but are not limited to,2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (e.g., LUPEROX 101™),dilauroyl peroxide (e.g. LUPEROX LP™), benzoyl peroxide (e.g., LUPEROXA98™), and bis(tert-butyldioxyisopropyl)benzene (e.g., VulCUP R™), etc.,including combinations thereof. Such organic peroxides are availablefrom a variety of sources, including but not limited to Arkema (420 rued'Estienne d'Orves, 92705 Colombes Cedex, France).

Elastomers.

A particularly useful embodiment for implementing the invention is forthe formation of elastomers. Tough, high-elongation elastomers aredifficult to achieve using only liquid UV-curable precursors. However,there exist many thermally cured materials (polyurethanes, silicones,natural rubber) that result in tough, high-elongation elastomers aftercuring. These thermally curable elastomers on their own are generallyincompatible with most 3D printing techniques.

In embodiments of the current invention, small amounts (e.g., less than20 percent by weight) of a low-viscosity UV curable material (Part A)are blended with thermally-curable precursors to form (preferably tough)elastomers (e.g. polyurethanes, polyureas, or copolymers thereof (e.g.,poly(urethane-urea)), and silicones) (Part B). The UV curable componentis used to solidify an object into the desired shape using 3D printingas described herein and a scaffold for the elastomer precursors in thepolymerizable liquid. The object can then be heated after printing,thereby activating the second component, resulting in an objectcomprising the elastomer.

Adhesion of Formed Objects.

In some embodiments, it may be useful to define the shapes of multipleobjects using the solidification of Part A, align those objects in aparticular configuration, such that there is a hermetic seal between theobjects, then activate the secondary solidification of Part B. In thismanner, strong adhesion between parts can be achieved during production.A particularly useful example may be in the formation and adhesion ofsneaker components.

Fusion of Particles as Part B.

In some embodiments, “Part B” may simply consist of small particles of apre-formed polymer. After the solidification of Part A, the object maybe heated above the glass transition temperature of Part B in order tofuse the entrapped polymeric particles.

Evaporation of solvent as Part B.

In some embodiments, “Part B” may consist of a pre-formed polymerdissolved in a solvent. After the solidification of Part A into thedesired object, the object is subjected to a process (e.g. heat+vacuum)that allows for evaporation of the solvent for Part B, therebysolidifying Part B.

Thermally Cleavable End Groups.

In some embodiments, the reactive chemistries in Part A can be thermallycleaved to generate a new reactive species after the solidification ofPart A. The newly formed reactive species can further react with Part Bin a secondary solidification. An exemplary system is described byVelankar, Pezos and Cooper, Journal of Applied Polymer Science. 62,1361-1376 (1996). Here, after UV-curing, the acrylate/methacrylategroups in the formed object are thermally cleaved to generateddiisocyanate prepolymers that further react with blended chain-extenderto give high molecular weight polyurethanes/polyureas within theoriginal cured material or scaffold. Such systems are, in general,dual-hardening systems that employ blocked or reactive blockedprepolymers, as discussed in greater detail below. It may be noted thatlater work indicates that the thermal cleavage above is actually adisplacement reaction of the chain extender (usually a diamine) with thehindered urea, giving the final polyurethanes/polyureas withoutgenerating isocyanate intermediates.

Methods of Mixing Components.

In some embodiments, the components may be mixed in a continuous mannerprior to being introduced to the printer build plate. This may be doneusing multi-barrel syringes and mixing nozzles. For example, Part A maycomprise or consist of a UV-curable di(meth)acrylate resin, Part B maycomprise or consist of a diisocyanate prepolymer and a polyol mixture.The polyol can be blended together in one barrel with Part A and remainunreacted. A second syringe barrel would contain the diisocyanate ofPart B. In this manner, the material can be stored without worry of“Part B” solidifying prematurely. Additionally, when the resin isintroduced to the printer in this fashion, a constant time is definedbetween mixing of all components and solidification of Part A.

Other Additive Manufacturing Techniques.

It will be clear to those skilled in the art that the materialsdescribed in the current invention will be useful in other additivemanufacturing techniques including fused deposition modeling (FDM),solid laser sintering (SLS), and Ink-jet methods. For example, amelt-processed acrylonitrile-butadiene-styrene resin may be formulatedwith a second UV-curable component that can be activated after theobject is formed by FDM. New mechanical properties could be achieved inthis manner. In another alternative, melt-processed unvulcanized rubberis mixed with a vulcanizing agent such as sulfur or peroxide, and theshape set through FDM, then followed by a continuation of vulcanization.

IV. Dual Hardening Polymerizable Liquids Employing Blocked Constituentsand Thermally Cleavable Blocking Groups.

In some embodiments, where the solidifying and/or curing step (d) iscarried out subsequent to the irradiating step (e.g., by heating ormicrowave irradiating); the solidifying and/or curing step (d) iscarried out under conditions in which the solid polymer scaffolddegrades and forms a constituent necessary for the polymerization of thesecond component (e.g., a constituent such as (i) a prepolymer, (ii) adiisocyanate or polyisocyanate, and/or (iii) a polyol and/or diol, wherethe second component comprises precursors to a polyurethane/polyurearesin). Such methods may involve the use of reactive or non-reactiveblocking groups on or coupled to a constituent of the first component,such that the constituent participates in the first hardening orsolidifying event, and when de-protected (yielding free constituent andfree blocking groups or blocking agents) generates a free constituentthat can participate in the second solidifying and/or curing event.Non-limiting examples of such methods are described further below.

A. Dual Hardening Polymerizable Liquids Employing Blocked Prepolymersand Thermally Cleavable Blocking Groups.

Some “dual cure” embodiments of the present invention are, in general, amethod of forming a three-dimensional object, comprising:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween:

(b) filling the build region with a polymerizable liquid, thepolymerizable liquid comprising a mixture of a blocked or reactiveblocked prepolymer, optionally but in some embodiments preferably areactive diluent, a chain extender, and a photoinitiator;

(c) irradiating the build region with light through the opticallytransparent member to form a (rigid, compressible, collapsible, flexibleor elastic) solid blocked polymer scaffold from the blocked prepolymerand optionally the reactive diluent while concurrently advancing thecarrier away from the build surface to form a three-dimensionalintermediate having the same shape as, or a shape to be imparted to, thethree-dimensional object, with the intermediate containing the chainextender; and then

(d) heating or microwave irradiating the three-dimensional intermediatesufficiently to form the three-dimensional product from thethree-dimensional intermediate (without wishing to be bound to anyparticular mechanism, the heating or microwave irradiating may cause thechain extender to react with the blocked or reactive blocked prepolymeror an unblocked product thereof).

In some embodiments, the blocked or reactive blocked prepolymercomprises a polyisocyanate.

In some embodiments, the blocked or reactive blocked prepolymercomprises a compound of the formula A-X-A, where X is a hydrocarbylgroup and each A is an independently selected substituent of Formula X:

where R is a hydrocarbyl group, R′ is O or NH, and Z is a blockinggroup, the blocking group optionally having a reactive terminal group(e.g., a polymerizable end group such as an epoxy, alkene, alkyne, orthiol end group, for example an ethylenically unsaturated end group suchas a vinyl ether).

In some embodiments, the blocked or reactive blocked prepolymercomprises a polyisocyanate oligomer produced by the reaction of at leastone diisocyanate (e.g., a diisocyanate such as hexamethylenediisocyanate (HDI), bis-(4-isocyanatocyclohexyl)methane (HMDI),isophorone diisocyanate (IPDI), etc., a triisocyanate, etc.) with atleast one polyol (e.g., a polyether or polyester or polybutadiene diol).

In some embodiments, the reactive blocked prepolymer is blocked byreaction of a polyisocyanate with an amine (meth)acrylate monomerblocking agent (e.g., tertiary-butylaminoethyl methacrylate (TBAEMA),tertiary pentylaminoethyl methacrylate (TPAEMA), tertiaryhexylaminoethyl methacrylate (THAEMA), tertiary-butylaminopropylmethacrylate (TBAPMA), acrylate analogs thereof, and mixtures thereof(see. e.g., US Patent Application Publication No. 20130202392). Notethat all of these can be used as diluents as well.

There are many blocking agents for isocyanate. In preferred embodimentsof the current invention, the blocking agent (e.g., TBAEMA), cures(e.g., from the actinic radiation or light) into the system. Thoseskilled in the art can couple (meth)acrylate groups to known blockingagents to create additional blocking agents that can be used to carryout the present invention. Still further, those skilled in the art canuse maleimide, or substitute maleimide on other known blocking agents,for use in the present invention.

Examples of known blocking agents which can be substituted on orcovalently coupled to (meth)acrylate or maleimide for use in the presentinvention include, but are not limited to, phenol type blocking agents(e.g. phenol, cresol, xylenol, nitrophenol, chlorophenol, ethyl phenol,t-butylphenol, hydroxy benzoic acid, hydroxy benzoic acid esters,2,5-di-t-butyl-4-hydroxy toluene, etc.), lactam type blocking agents(e.g. ε-caprolactam. δ-valerolactam, γ-butyrolactam, β-propiolactam,etc.), active methylene type blocking agents (e.g. diethyl malonate,dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone, etc.), alcohol type blocking agents (e.g. methanol, ethanol,n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-amylalcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,propylene glycol monomethyl ether, methoxyethanol, glycolic acid,glycolic acid esters, lactic acid, lactic acid ester, methylol urea,methylol melamine, diacetone alcohol, ethylene chlorohydrine, ethylenebromhydrine, 1,3-dichloro-2-propanol, ω-hydroperfluoro alcohol,acetocyanhydrine, etc.), mercaptan type blocking agents (e.g. butylmercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan,2-mercapto-benzothiazole, thiophenol, methyl thiophenol, ethylthiophenyl, etc.), acid amide type blocking agents (e.g. acetoanilide,acetoanisidine amide, acrylamide, methacrylamide, acetic amide, stearicamide, benzamide, etc.), imide type blocking agents (e.g. succinimide,phthalimide, maleimide, etc.), amine type blocking agents (e.g.diphenylamine, phenylnaphthylamine, xylidine, N-phenyl xylidine,carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine, etc.), imidazole type blocking agents (e.g. imidazole,2-ethylimidazole, etc.), urea type blocking agents (e.g. urea, thiourea,ethylene urea, ethylene thiourea, 1,3-diphenyl urea, etc.), carbamatetype blocking agents (e.g. N-phenyl carbamic acid phenyl ester,2-oxazolidone, etc.), imine type blocking agents (e.g. ethylene imine,etc.), oxime type blocking agents (e.g. formaldoxime, acetaldoximine,acetoxime, methylethyl ketoxime, diacetylomonoxime, benzophenoxime,cyclohexanonoxime, etc.) and sulfurous acid salt type blocking agents(e.g. sodium bisulfite, potassium bisulfite, etc.). Of these, use ispreferably made of the phenol type, the lactam type, the activemethylene type and the oxime type blocking agents (see. e.g., U.S. Pat.No. 3,947,426).

In some embodiments, the diisocyanate or isocyanate-functional oligomeror prepolymer is blocked with an aldehyde blocking agent, such as aformyl blocking agent. Examples include but are not limited to2-formyloxyethyl (meth)acrylate (FEMA) or other aldehyde-containingacrylate or methacrylate) with a diisocyanate or isocyanate functionaloligomer or polymer. See, e.g., X. Tassel et al., A New Blocking Agentof isocyanates. European Polymer Journal 36(9), 1745-1751 (2000); T.Haig. P. Badyrka et al., U.S. Pat. No. 8,524,816; and M. Sullivan and D.Bulpett, U.S. Pat. Appl. Pub. No. US20120080824 The reaction product ofsuch an aldehyde blocking agent and an isocyanate can in someembodiments possess an advantage over TBAEMA blocked ABPUs by reducinghydrogen bonding due to urea formation, in turn (in some embodiments)resulting in lower viscosity blocked isocvanates. In addition, in someembodiments, a second advantage is eliminating free amines within thefinal product (a product of the deblocking of TBAEMA from the ABPU)which might oxidize and cause yellowness or lead to degradation.

In some embodiments, the reactive diluent comprises an acrylate, amethacrylate, a styrene, an acrylic acid, a vinylamide, a vinyl ether, avinyl ester (including derivatives thereof), polymers containing any oneor more of the foregoing, and combinations of two or more of theforegoing. (e.g., acrylonitrile, styrene, divinyl benzene, vinyltoluene, methyl acrylate, ethyl acrylate, butyl acrylate, methyl(meth)acrylate, amine (meth)acrylates as described above, and mixturesof any two or more of these) (see, e.g., US Patent ApplicationPublication No. 20140072806).

In some embodiments, the chain extender comprises at least one diol,diamine or dithiol chain extender (e.g., ethylene glycol,1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol,1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, the correspondingdiamine and dithiol analogs thereof, lysine ethyl ester, arginine ethylester, p-alanine-based diamine, and random or block copolymers made fromat least one diisocyanate and at least one diol, diamine or dithiolchain extender; see. e.g., US Patent Application Publication No.20140010858). Note also that, when dicarboxylic acid is used as thechain extender, polyesters (or carbamate-carboxylic acid anhydrides) aremade.

In some embodiments, the polymerizable liquid comprises:

from 5 or 20 or 40 percent by weight to 60 or 80 or 90 percent by weightof the blocked or reactive blocked prepolymer;

from 10 or 20 percent by weight to 30 or 40 or 50 percent by weight ofthe reactive diluent;

from 5 or 10 percent by weight to 20 or 30 percent by weight of thechain extender; and

from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent by weight of thephotoinitiator. Optional additional ingredients, such as dyes, fillers(e.g., silica), surfactants, etc., may also be included, as discussed ingreater detail above.

An advantage of some embodiments of the invention is that, because thesepolymerizable liquids do not rapidly polymerize upon mixing, they may beformulated in advance, and the filling step carried out by feeding orsupplying the polymerizable liquid to the build region from a singlesource (e.g., a single reservoir containing the polymerizable liquid inpre-mixed form), thus obviating the need to modify the apparatus toprovide separate reservoirs and mixing capability.

Three-dimensional objects made by the process are, in some embodiments,collapsible or compressible (that is, elastic (e.g., has a Young'smodulus at room temperature of from about 0.001, 0.01 or 0.1 gigapascalsto about 1, 2 or 4 gigapascals, and/or a tensile strength at maximumload at room temperature of about 0.01, 0.1, or 1 to about 50, 100, or500 megapascals, and/or a percent elongation at break at roomtemperature of about 10, 20 50 or 100 percent to 1000, 2000, or 5000percent, or more).

In some embodiments, the dual cure resin is comprised of a UV-curable(meth)acrylate blocked polyurethane (ABPU), a reactive diluent, aphotoinitiator, and a chain extender(s). The reactive diluent (10-50 wt%) is an acrylate or methacrylate that helps to reduce the viscosity ofABPU and will be copolymerized with the ABPU under UV irradiation. Thephotoinitiator (generally about 1 wt %) can be one of those commonlyused UV initiators, examples of which include but are not limited tosuch as acetophenones (diethoxyacetophenone for example), phosphineoxides diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide,phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (PPO), Irgacure 369,etc.

After UV curing to form a intermediate shaped product having blockedpolyurethane oligomers as a scaffold, and carrying the chain extender,the ABPU resin is subjected to a thermal cure, during which a highmolecular weight polyurethane/polyurea is formed by a spontaneousreaction between the polyurethane/polyurea oligomers and the chainextender(s). The polyurethane/polyurea oligomer can react with properchain extenders through substitution of TBAEMA, N-vinylformamide (NVF)or the like by proper chain extenders, either by deblocking ordisplacement. The thermal cure time needed can vary depending on thetemperature, size, shape, and density of the product, but is typicallybetween 1 to 6 hours depending on the specific ABPU systems, chainextenders and temperature.

One advantageous aspect of the foregoing is using a tertiaryamine-containing (meth)acrylate (e.g., t-butylaminoethyl methacrylate,TBAEMA) to terminate synthesized polyurethane/polyurea oligomers withisocyanate at both ends. Using acrylate or methacrylate containinghydroxyl groups to terminate polyurethane/polyurea oligomers withisocyanate ends is used in UV curing resins in the coating field. Theformed urethane bonds between the isocyanate and hydroxyl groups aregenerally stable even at high temperatures. In embodiments of thepresent invention, the urea bond formed between the tertiary amine ofTBAEMA and isocyanate of the oligomer becomes labile when heated tosuitable temperature (for example, about 100° C.), regenerating theisocyanate groups that will react with the chain extender(s) duringthermal-cure to form high molecular weight polyurethane (PU). While itis possible to synthesize other (meth)acrylate containing isocyanateblocking functionality as generally used (such as N-vinylformamide,ε-caprolactam, 1,2,3-triazole, methyl ethyl ketoxime, diethyl malonate,etc.), the illustrative embodiment uses TBAEMA that is commerciallyavailable. The used chain extenders can be diols, diamines, triols,triamines or their combinations or others. Ethylene glycol,1,4-butanediol, methylene dicyclohexylamine (H12MDA; or PACM as thecommercial name from Air Products), hydroquinone bis(2-Hydroxyethyl)Ether (HQEE), 4,4′-Methylenebis(3-Chloro-2,6-Diethylaniline) (MCDEA),4,4′-methylene-bis-(2,6 diethylaniline)(MDEA),4,4′-Methylenebis(2-chloroaniline) (MOCA) are the preferred chainextenders.

To produce an ABPU, TBAEMA may be used to terminate the isocyanate endgroups of the prepolymer, which is derived from isocyanate tippedpolyols. The polyols (preferably with hydroxyl functionality of 2) usedcan be polyethers [especially polytetramethylene oxide (PTMO),polypropylene glycol (PPG)], polyesters [polycaprolactone (PCL),polycarbonate, etc.], polybutadiene and block copolymers such as PCL andPTMO block copolymer (Capa 7201A of Perstop, Inc.). The molecular weightof these polyols can be 500 to 6000 Da, and 500-2000 Da are preferred.In the presence of a catalyst (e.g., stannous octoate with 0.1-0.3 wt %to the weight of polyol; other tin catalysts or amine catalysts),diisocyanate (e.g., toluene diisocyanate (TDI), methylene diphenyldiisocyanate (MDI), hexamethylene diisocyanate (HDI), isophoronediisocyanate (IPDI), hydrogenated MDI (HMDI), para-phenyl diisocyanate(PPDI) etc.) is added to the polyol (or the reverse order; preferablythe polyol being added to the isocyanate) with certain molar ratio(larger than 1:1; preferably, no less than 2:1 and 2:1 is mostlypreferred) to make a prepolymer with residual isocyanate groups (50˜100°C.). TBAEMA is then added to the reaction [Note:moles(TBAEMA)*2+moles(OH)=moles(isocyanate)] to cap the remainingisocyanate groups, resulting in ABPU (under 40-70° C.). Radicalinhibitors such as hydroquinone (100-500 ppm) can be used to inhibitpolymerization of (meth)acrylate during the reaction.

In general, a three-dimensional product of the foregoing methodscomprises (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), or (iii) combinations thereof (optionally blendedwith de-blocked blocking group which is copolymerized with the reactivediluents(s), for example as an interpenetrating polymer network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network)). In some example embodiments, thethree-dimensional product may also include unreacted photoinitiatorremaining in the three-dimensional formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount. In example embodiments, athree-dimensional product may comprise, consist of or consistessentially of all or any combination of a linear thermoplasticpolyurethane, a cross-linked thermoset polyurethane, unreactedphotoinitiator and reacted photoinitiator materials.

While this embodiment has been described above primarily with respect toreactive blocking groups, it will be appreciated that unreactiveblocking groups may be employed as well.

In addition, while less preferred, it will be appreciated that processesas described above may also be carried out without a blocking agent,while still providing dual cure methods and products of the presentinvention.

In addition, while this embodiment has been described primarily withdiol and diamine chain extenders, it will be appreciated that chainextenders with more than two reactive groups (polyol and polyamine chainextenders such as triols and triamine chain extenders) may be used tothree-dimensional objects comprised of a crosslinked thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)).

These materials may be used in bottom-up additive manufacturingtechniques such as the continuous liquid interface printing techniquesdescribed herein, or other additive manufacturing techniques as notedabove and below.

B. Dual Hardening Polymerizable Liquids Employing Blocked Diisocyanatesand Thermally Cleavable Blocking Groups.

Another embodiment provides a method of forming a three-dimensionalobject comprised of polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), the method comprising:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween;

(b) filling the build region with a polymerizable liquid, thepolymerizable liquid comprising a mixture of (i) a blocked or reactiveblocked diisocyanate, (ii) a polyol and/or polyamine, (iii) a chainextender, (iv) a photoinitiator, and (v) optionally but in someembodiments preferably a reactive diluent (vi) optionally but in someembodiments preferably a pigment or dye. (vii) optionally but in someembodiments preferably a filler (e.g. silica),

(c) irradiating the build region with light through the opticallytransparent member to form a solid blocked diisocyanate scaffold fromthe blocked diisocyanate, and optionally the reactive diluent andadvancing the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object, with the intermediatecontaining the chain extender and polyol and/or polyamine; and then

(d) heating or microwave irradiating the three-dimensional intermediatesufficiently (e.g., sufficiently to de-block the blocked diisocyanateand form an unblocked diisocyanate that in turn polymerizes with thechain extender and polyol and/or polyamine) to form thethree-dimensional product comprised of polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), from thethree-dimensional intermediate.

In some embodiments, the blocked or reactive blocked diisocyanatecomprises a compound of the formula A′-X′-A′, where X′ is a hydrocarbylgroup and each A′ is an independently selected substituent of Formula(X′):

where Z is a blocking group, the blocking group optionally having areactive terminal group (e.g., a polymerizable end group such as anepoxy, alkene, alkyne, or thiol end group, for example an ethylenicallyunsaturated end group such as a vinyl ether).

In general, a three-dimensional product of the foregoing methodscomprises (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), a(ii) cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), or (iii) combinations thereof (optionally blendedwith de-blocked blocking group which is copolymerized with the reactivediluents(s), for example as an interpenetrating polymer network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network). In some example embodiments, thethree-dimensional product may also include unreacted photoinitiatorremaining in the three-dimensional formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount. In example embodiments, athree-dimensional product may comprise, consist of or consistessentially of all or any combination of a linear thermoplasticpolyurethane, a cross-linked thermoset polyurethane, unreactedphotoinitiator and reacted photoinitiator materials.

While this embodiment has been described above primarily with respect toreactive blocking groups, it will be appreciated that unreactiveblocking groups may be employed as well.

In addition, while less preferred, it will be appreciated that processesas described above may also be carried out without a blocking agent,while still providing dual cure methods and products of the presentinvention.

In addition, while this embodiment has been described primarily withdiol and diamine chain extenders, it will be appreciated that chainextenders with more than two reactive groups (polyol and polyamine chainextenders such as triols and triamine chain extenders) may be used tothree-dimensional objects comprised of a crosslinked thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)).

These materials may be used in bottom-up additive manufacturingtechniques such as the continuous liquid interface printing techniquesdescribed herein, or other additive manufacturing techniques as notedabove and below.

C. Dual Hardening Polymerizable Liquids Employing Blocked ChainExtenders and Thermally Cleavable Blocking Groups.

Another embodiment provides a method of forming a three-dimensionalobject comprised of polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), the method comprising:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween:

(b) filling the build region with a polymerizable liquid, thepolymerizable liquid comprising a mixture of (i) a polyol and/orpolyamine, (ii) a blocked or reactive blocked diisocyanate chainextender, (ii) optionally one or more additional chain extenders, (iv) aphotoinitiator, and (v) optionally but in some embodiments preferably areactive diluent (vi) optionally but in some embodiments preferably apigment or dye, (vii) optionally but in some embodiments preferably afiller (e.g., silica);

(c) irradiating the build region with light through the opticallytransparent member to form a solid blocked chain diisocvanate chainextender scaffold from the blocked or reactive blocked diisocyanatechain extender and optionally the reactive diluent and advancing thecarrier away from the build surface to form a three-dimensionalintermediate having the same shape as, or a shape to be imparted to, thethree-dimensional object, with the intermediate containing the polyoland/or polyamine and optionally one or more additional chain extenders;and then

(d) heating or microwave irradiating the three-dimensional intermediatesufficiently to form the three-dimensional product comprised ofpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), from the three-dimensional intermediate (e.g.,heating or microwave irradiating sufficiently to de-block the blockeddiisocyanate chain extender to form an unblocked diisocyanate chainextender that in turn polymerizes with the polyol and/or polyamine andoptionally one or more additional chain extenders).

In some embodiments, the blocked or reactive blocked diisocyanate chainextender comprises a compound of the formula A″-X″-A″, where X″ is ahydrocarbyl group, and each A″ is an independently selected substituentof Formula (X″):

where R is a hydrocarbyl group, R′ is O or NH, and Z is a blockinggroup, the blocking group optionally having a reactive terminal group(e.g., a polymerizable end group such as an epoxy, alkene, alkyne, orthiol end group, for example an ethylenically unsaturated end group suchas a vinyl ether).

In general, a three-dimensional product of the foregoing methodscomprises (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)), (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), or (iii) combinations thereof (optionally blendedwith de-blocked blocking group which is copolymerized with the reactivediluents(s), for example as an interpenetrating polymer network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network). In some example embodiments, thethree-dimensional product may also include unreacted photoinitiatorremaining in the three-dimensional formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount. In example embodiments, athree-dimensional product may comprise, consist of or consistessentially of all or any combination of a linear thermoplasticpolyurethane, a cross-linked thermoset polyurethane, unreactedphotoinitiator and reacted photoinitiator materials.

While this embodiment has been described above primarily with respect toreactive blocking groups (that is, blocking groups containingpolymerizable moieties), it will be appreciated that unreactive blockinggroups may be employed as well.

In addition, while less preferred, it will be appreciated that processesas described above may also be carried out without a blocking agent,while still providing dual cure methods and products of the presentinvention.

In addition, while this embodiment has been described primarily withdiol and diamine chain extenders, it will be appreciated that chainextenders with more than two reactive groups (polyol and polyamine chainextenders such as triols and triamine chain extenders) may be used toform three-dimensional objects comprised of a crosslinked thermosetpolyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)).

These materials may be used in bottom-up additive manufacturingtechniques such as the continuous liquid interface printing techniquesdescribed herein, or other additive manufacturing techniques as notedabove and below.

Those skilled in the art will appreciate that systems as described inYing and Cheng, Hydrolyzable Polyureas Bearing Hindered Urea Bonds, JACS136, 16974 (2014), may be used in carrying out the methods describedherein.

V. Articles Comprised of Interpenetrating Polymer Networks (IPNs) Formedfrom Dual Hardening Polymerizable Liquids.

In some embodiments, polymerizable liquids comprising dual hardeningsystems such as described above are useful in forming three-dimensionalarticles that in turn comprise interpenetrating polymer networks. Thisarea has been noted by Sperling at Lehigh University and K. C. Frisch atthe University of Detroit, and others.

In non-limiting examples, the polymerizable liquid and method steps areselected so that the three-dimensional object comprises the following:

Sol-Gel Compositions.

This may be carried out with an amine (ammonia) permeable window orsemipermeable member. In the system discussed here, tetraethylorthosiliciate (TEOS), epoxy (diglycidyl ether of Bisphenol A), and4-amino propyl triethoxysilane are be added to a free radicalcrosslinker and in the process the free radical crosslinker polymerizesand contain the noted reactants which are then reacted in another stepor stage. Reaction requires the presence of water and acid. Photoacidgenerators (PAGs) could optionally be added to the mixture describedabove to promote the reaction of the silica based network. Note that ifonly TEOS is included one will end up with a silica (glass) network. Onecould then increase the temperature to remove the organic phase and beleft with a silica structure that would be difficult to prepare by moreconventional methods. Many variations (different polymeric structures)can be prepared by this process in addition to epoxies includingurethanes, functionalized polyols, silicone rubber etc.)

Hydrophobic-Hydrophilic IPNs.

Prior IPN research contained a number of examples forhydrophobic-hydrophilic networks for improved blood compatibility aswell as tissue compatibility for biomedical parts. Poly(hydroxyethyl(meth)acrylate) is a typical example of a hydrophilic component. Anotheroption is to added poly(ethylene oxide) polyols or polyamines with adiisocyanate to produce polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)), incorporated in the reactive system.

Phenolic Resins (Resoles).

Precursors to phenolic resins involve either phenolic resoles(formaldehyde terminal liquid oligomers) or phenolic novolacs (phenolterminal solid oligomers crosslinkable with hexamethyltetraamine). Forthe present process phenolic resoles can be considered. The viscositythereof may be high but dilution with alcohols (methanol or ethanol) maybe employed. Combination of the phenolic resole with the crosslinkablemonomer can then provide a product formed from an IPN. Reaction of thephenolic resole to a phenolic resin can occur above 100° in a short timerange. One variation of this chemistry would be to carbonize theresultant structure to carbon or graphite. Carbon or graphite foam istypically produced from phenolic foam and used for thermal insulation athigh temperatures.

Polyimides.

Polyimides based on dianhydrides and diamines are amenable to thepresent process. In this case the polyimide monomers incorporated intothe reactive crosslinkable monomer are reacted to yield an IPNstructure. Most of the dianhydrides employed for polyimides may becrystalline at room temperature but modest amounts of a volatile solventcan allow a liquid phase. Reaction at modest temperatures (e.g., in therange of about 100° C.) is possible to permit polyimide formation afterthe network is polymerized.

Conductive Polymers.

The incorporation of aniline and ammonium persulfate into thepolymerizable liquid is used to produce a conductive part. After thereactive system is polymerized and a post treatment with acid (such asHCl vapor), polymerization to polyaniline can then commence.

Natural Product Based IPNs.

Numerous of natural product based IPNs are known based on triglycerideoils such as castor oil. These can be incorporated into thepolymerizable liquid along with a diisocyanate. Upon completion of thepart the triglycerides can then be reacted with the diisocyanate to forma crosslinked polyurethane. Glycerol can of course also be used.

Sequential IPNs.

In this case, the molded crosslinked network are swollen with a monomerand free radical catalyst (peroxide) and optionally crosslinker followedby polymerization. The crosslinked triacylate system should imbide largeamounts of styrene, acrylate and/or methacrylate monomers allowing asequential IPN to be produced.

Polyolefin Polymerization.

Polyolefin catalysts (e.g. metallocenes) can be added to thecrosslinkable reactive system. Upon exposure of the part to pressurizedethylene (or propylene) or a combination (to produce EPR rubber) andtemperature in the range of 100° C.) the part can then contain amoderate to substantial amount of the polyolefin. Ethylene, propyleneand alpha olefin monomers should easily diffuse into the part to reactwith the catalyst at this temperature and as polymerization proceedsmore olefin will diffuse to the catalyst site. A large number of partscan be post-polymerized at the same time.

VI. Fabrication Products.

A. Example Three-Dimensional (3D) Objects.

Three-dimensional products produced by the methods and processes of thepresent invention may be final, finished or substantially finishedproducts, or may be intermediate products subject to furthermanufacturing steps such as surface treatment, laser cutting, electricdischarge machining, etc., is intended. Intermediate products includeproducts for which further additive manufacturing, in the same or adifferent apparatus, may be carried out). For example, a fault orcleavage line may be introduced deliberately into an ongoing “build” bydisrupting, and then reinstating, the gradient of polymerization zone,to terminate one region of the finished product, or simply because aparticular region of the finished product or “build” is less fragilethan others.

Numerous different products can be made by the methods and apparatus ofthe present invention, including both large-scale models or prototypes,small custom products, miniature or microminiature products or devices,etc. Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,functional structures, microneedle arrays, fibers and rods such aswaveguides, micromechanical devices, microfluidic devices, etc.

Thus in some embodiments the product can have a height of from 0.1 or 1millimeters up to 10 or 100 millimeters, or more, and/or a maximum widthof from 0.1 or 1 millimeters up to 10 or 100 millimeters, or more. Inother embodiments, the product can have a height of from 10 or 100nanometers up to 10 or 100 microns, or more, and/or a maximum width offrom 10 or 100 nanometers up to 10 or 100 microns, or more. These areexamples only: Maximum size and width depends on the architecture of theparticular device and the resolution of the light source and can beadjusted depending upon the particular goal of the embodiment or articlebeing fabricated.

In some embodiments, the ratio of height to width of the product is atleast 2:1, 10:1, 50:1, or 100:1, or more, or a width to height ratio of1:1, 10:1, 50:1, or 100:1, or more.

In some embodiments, the product has at least one, or a plurality of,pores or channels formed therein, as discussed further below.

The processes described herein can produce products with a variety ofdifferent properties. Hence in some embodiments the products are rigid;in other embodiments the products are flexible or resilient. In someembodiments, the products are a solid; in other embodiments, theproducts are a gel such as a hydrogel. In some embodiments, the productshave a shape memory (that is, return substantially to a previous shapeafter being deformed, so long as they are not deformed to the point ofstructural failure). In some embodiments, the products are unitary (thatis, formed of a single polymerizable liquid); in some embodiments, theproducts are composites (that is, formed of two or more differentpolymerizable liquids). Particular properties will be determined byfactors such as the choice of polymerizable liquid(s) employed.

In some embodiments, the product or article made has at least oneoverhanging feature (or “overhang”), such as a bridging element betweentwo supporting bodies, or a cantilevered element projecting from onesubstantially vertical support body. Because of the unidirectional,continuous nature of some embodiments of the present processes, theproblem of fault or cleavage lines that form between layers when eachlayer is polymerized to substantial completion and a substantial timeinterval occurs before the next pattern is exposed, is substantiallyreduced. Hence, in some embodiments the methods are particularlyadvantageous in reducing, or eliminating, the number of supportstructures for such overhangs that are fabricated concurrently with thearticle.

B. Example Structures and Geometries of 3D Objects.

In example embodiments, the three-dimensional (3D) object may be formedwith thousands or millions of shape variations imparted on thethree-dimensional object while being formed. In example embodiments, thepattern generator generates different patterns of light to activatephotoinitiator in the region of the gradient of polymerization to impartdifferent shapes as the object is extracted through the gradient ofpolymerization. In example embodiments, the pattern generator may havehigh resolution with millions of pixel elements that can be varied tochange the shape that is imparted. For example, the pattern generatormay be a DLP with more than 1,000 or 2,000 or 3,000 or more rows and/ormore than 1.000 or 2,000 or 3,000 or more columns of micromirrors, orpixels in an LCD panel, that can be used to vary the shape. As a result,very fine variations or gradations may be imparted on the object alongits length. In example embodiments, this allows complexthree-dimensional objects to be formed at high speed with asubstantially continuous surface without cleavage lines or seams. Insome examples, more than a hundred, thousand, ten thousand, hundredthousand or million shape variations may be imparted on thethree-dimensional object being formed without cleavage lines or seamsacross a length of the object being formed of more than 1 mm, 1 cm, 10cm or more or across the entire length of the formed object. In exampleembodiments, the object may be continuously formed through the gradientof polymerization at a rate of more than 1, 10, 100, 1000, 10000 or moremicrons per second.

In example embodiments, this allows complex three-dimensional (3D)objects to be formed. In some example embodiments, the 3D formed objectshave complex non-injection moldable shapes. The shapes may not becapable of being readily formed using injection molding or casting. Forexample, the shapes may not be capable of being formed by discrete moldelements that are mated to form a cavity in which fill material isinjected and cured, such as a conventional two-part mold. For example,in some embodiments, the 3D formed objects may include enclosed cavitiesor partially open cavities, repeating unit cells, or open-cell orclosed-cell foam structures that are not amenable to injection moldingand may including hundreds, thousands or millions of these structures orinterconnected networks of these structures. However, in exampleembodiments, these shapes may be 3D formed using the methods describedin the present application with a wide range of properties, including awide range of elastomeric properties, tensile strength and elongation atbreak through the use of dual cure materials and/or interpenetratingpolymer networks to form these structures. In example embodiments, the3D objects may be formed without cleavage lines, parting lines, seams,sprue, gate marks or ejector pin marks that may be present withinjection molding or other conventional techniques. In some embodiments,the 3D formed objects may have continuous surface texture (whethersmooth, patterned or rough) that is free from molding or other printingartifacts (such as cleavage lines, parting lines, seams, sprue, gatemarks or ejector pin marks) across more than 1 mm, 1 cm, 10 cm or moreor across the entire length of the formed object. In exampleembodiments, complex 3D objects may be formed with no discrete layersvisible or readily detectable from the printing process in the finished3D object across more than 1 mm, 1 cm, 10 cm or more or across theentire length of the formed object. For example, the varying shapesimparted during the course of printing by the pattern generator may notbe visible or detectable as different layers in the finished 3D objectsince the printing occurs through the gradient of polymerization zone(from which the 3D object is extracted as it is exposed by varyingpatterns projected from the pattern generator). While the 3D objectsresulting from this process may be referred to as 3D printed objects,the 3D objects may be formed through continuous liquid interphaseprinting without the discrete layers or cleavage lines associated withsome 3D printing processes.

In some embodiments, the 3D formed object may include one or morerepeating structural elements to form the 3D objects, including, forexample, structures that are (or substantially correspond to) enclosedcavities, partially-enclosed cavities, repeating unit cells or networksof unit cells, foam cell, Kelvin foam cell or other open-cell orclosed-cell foam structures, crisscross structures, overhang structures,cantilevers, microneedles, fibers, paddles, protrusions, pins, dimples,rings, tunnels, tubes, shells, panels, beams (including 1-beams,U-beams, W-beams and cylindrical beams), struts, ties, channels (whetheropen, closed or partially enclosed), waveguides, triangular structures,tetrahedron or other pyramid shape, cube, octahedron, octagon prism,icosidodecahedron, rhombic triacontahedron or other polyhedral shapes ormodules (including Kelvin minimal surface tetrakaidecahedra, prisms orother polyhedral shapes), pentagon, hexagonal, octagon and other polygonstructures or prisms, polygon mesh or other three-dimensional structure.In some embodiments, a 3D formed object may include combinations of anyof these structures or interconnected networks of these structures. Inan example embodiments, all or a portion of the structure of the 3Dformed object may correspond (or substantially correspond) to one ormore Bravais lattice or unit cell structures, including cubic (includingsimple, body-centered or face-centered), tetragonal (including simple orbody-centered), monoclinic (including simple or end-centered),orthohombic (including simple, body-centered, face-centered orend-centered), rhombohedral, hexagonal and triclinic structures. Inexample embodiments, the 3D formed object may include shapes or surfacesthat correspond (or substantially correspond) to a catenoid, helicoid,gyroid or lidinoid, other triply periodic minimal surface (TPMS), orother geometry from the associate family (or Bonnet family) or Schwarz P(“Primitive”) or Schwarz D (“Diamond”), Schwarz H (“Hexagonal”) orSchwarz CLP (“Crossed layers of parallels”) surfaces, argyle or diamondpatterns, lattice or other pattern or structure.

In example embodiments, the pattern generator may be programmed to varyrapidly during printing to impart different shapes into the gradient ofpolymerization with high resolution. As a result, any of the abovestructural elements may be formed with a wide range of dimensions andproperties and may be repeated or combined with other structuralelements to form the 3D object. In example embodiments, the 3D formedobject may include a single three-dimensional structure or may includemore than 1, 10, 100, 1000, 10000, 100000, 1000000 or more of thesestructural elements. The structural elements may be repeated structuralelements of similar shapes or combinations of different structuralelements and can be any of those described above or other regular orirregular shapes. In example embodiments, each of these structuralelements may have a dimension across the structure of at least 10nanometers, 100 nanometers, 10 microns, 100 microns, 1 mm, 1 cm, 10 cm,50 cm or more or may have a dimension across the structure of less than50 cm, 10 cm, 1 cm, 1 mm, 100 microns, 10 microns, 100 nanometers or 10nanometers or less. In example embodiments, a height, width or otherdimension across the structure may be in the range of from about 10nanometers to about 50 cm or more or any range subsumed therein. As usedherein, “any range subsumed therein” means any range that is within thestated range. For example, the following are all subsumed within therange of about 10 nanometers to about 50 square cm and are includedherein: 10 nanometers to 1 micron; 1 micron to 1 millimeter; 1millimeter to 1 centimeter; and 1 centimeter to 50 cm or any other rangeor set of ranges within the stated range. In example embodiments, eachof the structural elements may form a volume of the 3D object in therange of from about 10 square nanometers to about 50 square cm or moreor any range subsumed therein. In example embodiments, each of thestructural elements may form a cavity or hollow region or gap betweensurfaces of the structural element having a dimension across the cavityor hollow region or gap in the range of from about 10 nanometers toabout 50 cm or more or any range subsumed therein or may define a volumewithin the expanse of the 3D formed object in the range of from about 10square nanometers to about 50 square cm or more or any range subsumedtherein.

The structural elements may be about the same size or the size may varythroughout the volume of the 3D formed object. The sizes may increase ordecrease from one side of the 3D formed object to another side(gradually or step-wise) or elements of different shapes may beintermixed in regular or irregular patterns (for example, a 3Delastomeric foam with varying sizes of open-cell and/or closed-cellcavities intermixed throughout the foam).

In some embodiments, the 3D formed objects may have irregular shapeswith overhangs, bridging elements or asymmetries or may otherwise havean offset center of gravity in the direction being formed. For example,the 3D formed object may be asymmetric. In example embodiments, the 3Dformed object may not have rotational symmetry around any axis or mayhave rotational symmetry only around a single axis. In exampleembodiments, the 3D formed object may not have reflectional symmetryaround any plane through the 3D formed object or may have reflectionalsymmetry only around a single plane. In example embodiments, the 3Dobject may have an offset center of gravity. For example, the center ofgravity of the 3D formed object may not be at the positional center ofthe object. In some examples, the center of gravity may not be locatedalong any central axis of the object. For example, the 3D formed objectmay be a shoe sole or insert that generally follows the contour of afoot. The shoe sole or insert may tilt to the right or left and havedifferent widths for the heel and toes. As a result, the 3D formedobject in this example will not have reflectional symmetry from side toside or front to back. However, it may have reflectional symmetry frombottom to top if it is a uniformly flat shoe sole or insert. In otherexamples, the shoe sole or insert may be flat on one side and becontoured to receive the arch of a foot on the other side and, as aresult, will not have reflectional symmetry from bottom to top either.Other 3D formed objects for wearable, prosthetic or anatomical shapes ordevices may have similar asymmetries and/or offset center of gravity.For example, a 3D formed object for a dental mold or dental implant maysubstantially conform to the shape of a tooth and may not havereflectional symmetry about any plane. In another example, a 3D formedcomponent for a wearable device may substantially conform to the shapeof a body party and have corresponding asymmetries, such as athleticwear such as a right or left contoured shin guard or foam padding orinsert for use between a hard shin guard or a helmet or other wearablecomponent and the human body. These are examples only and any number of3D formed objects may be asymmetric and/or have an offset center ofgravity. In example embodiments, where there are significant asymmetriesor protruding elements (such as arms, bridging elements, cantilevers,brush fibers or the like) and the desired structural elements will beelastomeric, there is a potential for deformation during 3D printing orsubsequent curing. For example, if a large amount of non-UV curableelastomeric resin material is included, gravity may cause deformationbefore final curing. While the scaffold formed from UV-curable materialduring 3D printing (from the initial cure in a dual cure process) helpslock-in the shape, some elastomeric compositions with highly asymmetricor protruding shapes may be susceptible to deformation. In some exampleembodiments, the UV curable material in the composition may be adjustedto form a more rigid scaffold to avoid deformation. In other exampleembodiments, objects with asymmetric shapes and/or offset center ofgravity may be formed in pairs (or in other combinations) withconnectors that are later removed, particularly if the 3D formed objectsor protruding elements are relatively long. In an example, anelastomeric 3D object may be formed along a length, and have anasymmetry, center of gravity offset and/or protruding element transverseto the length that is more than 10%, 20%, 30%, 40%, 50% or more of thelength. For example, the 3D formed object may have a length of about 1cm to 50 cm or more or any range subsumed therein and may have atransverse or lateral asymmetry or protruding element of about 1 cm to50 cm or more or any range subsumed therein. In an example embodiment,two or more of these objects may be formed together in a way thatprovides support for the transverse or protruding elements until theelastomeric material is cured and the objects are separated. Forexample, two shoe soles may be formed (e.g., when formed in thedirection of their length) as a pair (for example, with rotated andinverted shoe soles formed together with small removable connectorsbetween them) such that the soles provide support to one another whilebeing formed. In other example embodiments, other support structures maybe formed and removed after curing of the elastomeric material.

C. Example Materials and Compositions of 3D Objects.

In example embodiments, 3D formed objects may have any of the aboveshapes or structures and may comprise or consist of or consistessentially of: (i) a linear thermoplastic polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)). (ii) a cross-linkedthermoset polyurethane, polyurea, or copolymer thereof (e.g.,poly(urethane-urea)), and/or (iii) combinations thereof (optionallyblended with de-blocked blocking group which is copolymerized with thereactive diluents(s), for example as an interpenetrating polymernetwork, a semi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network), and/or (iv) photoinitiator, includingunreacted photoinitiator and/or reacted photoinitiator fragments.

In some example embodiments, a silicone rubber 3D object may be formed.

1. Silicone Polyurethanes, Polyureas, or Poly(Urethane-Ureas).

In any of the preceding polyurethane examples, silicone orpoly(dimethylsiloxane) (PDMS) may be used as soft segment in theformation of these materials. For example, a (meth)acrylate-functionalABPU could be formed by first reacting an oligomeric PDMS diol ordiamine with two equivalents of diisocyanate to form a PDMS urethaneprepolymer. This material can be further reacted with TBAEMA or otherreactive blocking agents described herein to form a reactive blockedPDMS prepolymer which could be blended with chain extenders and reactivediluents as described in the examples above.

2. Silicone Interpenetrating Polymer Networks.

In some embodiments, the material may comprise, consists of or consistessentially of a UV-curable PDMS oligomer that is blended with atwo-part thermally curable PDMS oligomer system.

In example embodiments, 3D formed objects may have any of the aboveshapes or structures and may comprise or consist of or consistessentially of:

-   -   (i) A thermoset silicone or PDMS network cured by        platinum-catalyzed hydrosilation, tin-catalyzed condensation        chemistry, or peroxide initiated chemistry.    -   (ii) A UV-curable reactive diluent that is miscible with        silicone thermoset oligomers prior to curing. Example: an        acrylate-functional PDMS oligomer.    -   (iii) combinations thereof (optionally blended with reactive        diluents(s), for example as an interpenetrating polymer network,        a semi-interpenetrating polymer network, or as a sequential        interpenetrating polymer network), and/or    -   (iv) photoinitiator, including unreacted photoinitiator and/or        reacted photoinitiator fragments.

In an example embodiment, Phenylbis(2 4 6-trimethylbenzoyl)phosphineoxide (PPO) is dissolved in isobornyl acrylate (IBA) with a THINKY™mixer. Methacryloxypropyl terminated polydimethylsiloxane (DMS-R31;Gelest Inc.) is added to the solution, followed by addition of SylgardPart A and Part B (Corning PDMS precursors), and then further mixed witha THINKY™ mixer to produce a homogeneous solution. The solution isloaded into an apparatus as described above and a three-dimensionalintermediate is produced by ultraviolet curing as described above. Thethree-dimensional intermediate is then thermally cured at 100° C. for 12hours to produce the final silicone rubber product.

3. Epoxy Interpenetrating Networks.

In some example embodiments, an epoxy 3D object may be formed. Inexample embodiments, 3D formed objects may have any of the above shapesor structures and may comprise or consist of or consist essentially of:

-   -   (i) A thermoset epoxy network cured by the reaction of a        diepoxide with a diamine. Optionally, co-reactants may also be        included for example: co-reactants including polyfunctional        amines, acids (and acid anhydrides), phenols, alcohols, and        thiols;    -   (ii) A UV-curable reactive diluent that is miscible with the        epoxy thermoset precursors prior to curing;    -   (iii) (combinations thereof (optionally blended with the        reactive diluents(s), for example as an interpenetrating polymer        network, a semi-interpenetrating polymer network, or as a        sequential interpenetrating polymer network), and/or    -   (iv) photoinitiator, including unreacted photoinitiator and/or        reacted photoinitiator fragments.

In an example embodiment: 10.018 g EpoxAcast 690 resin part A and 3.040g part B is mixed on a THINKY™ mixer, 3.484 g is then mixed with 3.013 gof RKPS-78-1, a 65/22/13 mix of SartomerCN9782/N-vinylpyrrolidone/diethyleneglycol diacrylate to give a clearblend which is cured under a Dymax ultraviolet lamp to produce anelastic 3D object.

In a second example embodiment, RKP11-10-1 containing 3.517 g of theabove epoxy and 3.508 g of RKP5-90-3 and 65/33/2/0.25 blend of SartomerCN2920/N-vinylcaprolactam/N-vinylpyrrolidone/PPO initiator is curedsimilarly to form a flexible 3D object.

In some example embodiments, the 3D formed object may include sol-gelcompositions, hydrophobic or hydrophilic compositions, phenolic resoles,cyanate esters, polyimides, conductive polymers, natural product basedIPNs, sequential IPNs and polyolefin as described above.

In example embodiments, 3D formed objects may have any of the shapes orstructures described above and may comprise or consist of or consistessentially of a plurality of different materials in different regionsof the 3D formed object with different tensile strength or other varyingproperties. In example embodiments, the differing materials may beselected from any of those describe above. In some example embodiments,the process of fabricating the product may be paused or interrupted oneor more times, to change the polymerizable liquid. In exampleembodiments, 3D formed objects may include multiple materials (whichmay, for example, be a thermoplastic or thermoset polyurethane,polyurea, or copolymer thereof or silicone rubber or epoxy orcombination of the foregoing) with different tensile strengths asdescribed further below. While a fault line or plane may be formed inthe intermediate by the interruption, if the subsequent polymerizableliquid is, in its second cure material, reactive with that of the first,then the two distinct segments of the intermediate will cross-react andcovalently couple to one another during the second cure (e.g., byheating or microwave irradiation). Thus, for example, any of thematerials described herein may be sequentially changed to form a producthaving multiple distinct segments with different tensile properties,while still being a unitary product with the different segmentscovalently coupled to one another.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) or silicone rubber or epoxy or combinationof the foregoing may comprise a majority of the 3D formed object byweight and may comprise more than 50%, 60%, 70%, 80% or 9-0% of the 3Dformed object by weight. In example embodiments, the polyurethane,polyurea, or copolymer thereof (e.g., poly(urethane-urea)) or siliconerubber or epoxy or combination of the foregoing may comprise or consistof or consist essentially of an interpenetrating network, asemi-interpenetrating polymer network, or as a sequentialinterpenetrating polymer network.

(i) Examples of Thermoplastic or Thermoset Polyurethane, Polyurea, orCopolymer Thereof (e.g., Poly(Urethane-Urea)).

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise a majority of the 3D formedobject by weight and may comprise more than 50%, 60%, 70%, 80% or 90% ofthe 3D formed object by weight.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of linear thermoplastic or thermoset polyurethane, polyurea,or copolymer thereof (e.g., poly(urethane-urea)). In exampleembodiments, the linear thermoplastic or cross-linked thermosetpolyurethane, polyurea, or copolymer thereof (e.g., poly(urethane-urea))may comprise a majority of the 3D formed object by weight and maycomprise more than 50%, 60%, 70%, 80% or 90% of the 3D formed object byweight.

In example embodiments, the polyurethane, polyurea or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of a polymer blend of (i) linear ethylenically unsaturatedblocking monomer copolymerized with reactive diluent and (ii) linearthermoplastic or cross-linked thermoset polyurethane, polyurea, orcopolymer thereof (e.g., poly(urethane-urea)). In example embodiments,the polymer blend may comprise a majority of the 3D formed object byweight and may comprise more than 50%, 60%, 70%, 80% or 90% of the 3Dformed object by weight. In example embodiments, the linearthermoplastic or cross-linked polyurethane, polyurea, or copolymerthereof (e.g., poly(urethane-urea)) may comprise or consist of orconsist essentially of linear poly(meth)acrylate.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of an interpenetrating network, a semi-interpenetratingpolymer network, or as a sequential interpenetrating polymer network ofethylenically unsaturated monomer and crosslinked or linearpolyurethane. In example embodiments, the network of ethylenicallyunsaturated monomer and crosslinked polyurethane may comprise a majorityof the 3D formed object by weight and may comprise more than 50%, 60%,70%, 80% or 90% of the 3D formed object by weight. In exampleembodiments, the linear thermoplastic or cross-linked thermosetpolyurethane, polyurea, or copolymer thereof (e.g., poly(urethane-urea))may comprise or consist of or consist essentially of crosslinkedpoly(meth)acrylate.

In example embodiments, the polyurethane, polyurea, or copolymer thereof(e.g., poly(urethane-urea)) may comprise or consist of or consistessentially of an interpenetrating network, a semi-interpenetratingpolymer network, or as a sequential interpenetrating polymer network ofethylenically unsaturated monomer and linear thermoplastic orcross-linked thermoset polyurethane. In example embodiments, the networkof ethylenically unsaturated monomer and linear thermoplastic orcrosslinked thermoset polyurethane may comprise a majority of the 3Dformed object by weight and may comprise more than 50%, 60%, 70%, 80% or90% of the 3D formed object by weight. In example embodiments, thelinear thermoplastic or cross-linked thermoset polyurethane, polyurea,or copolymer thereof (e.g., poly(urethane-urea)) may comprise or consistof or consist essentially of linear poly(meth)acrylate.

In some example embodiments, the 3D formed object may include sol-gelcompositions, hydrophobic or hydrophilic compositions, phenolic resoles,cyanate esters, polyimides, conductive polymers, natural product basedIPNs, sequential IPNs and polyolefin as described above.

(ii) Example Photoinitiator and Photoinitiator Fragments.

In example embodiments, the 3D formed object may include unreactedphotoinitiator remaining in the 3D formed object. For example, in someembodiments, from 0.1 or 0.2 percent by weight to 1, 2 or 4 percent byweight of the photoinitiator may remain in the three-dimensional formedobject or the photoinitiator may be present in lower amounts or only atrace amount. In some example embodiments, the three-dimensional productmay also include reacted photoinitiator fragments. For example, in someembodiments, the reacted photoinitiator fragments may be remnants of thefirst cure forming the intermediate product. For example, from 0.1 or0.2 percent by weight to 1, 2 or 4 percent by weight of reactedphotoinitiator fragments may remain in the three-dimensional formedobject or the reacted photoinitiator fragments may be present in loweramounts or only a trace amount.

In example embodiments, because the systems, in part, consist ofmonomers and oligomers capable of being polymerized by exposure to UVlight, the end products will contain residual photoinitiator moleculesand photoinitiator fragments.

In some embodiments, a photopolymerization will undergo thetransformation outlined below. In the first step, initiation, UV lightcleaves the initiator into active radical fragments. These activeradical fragments will go on to react with monomer group “M.” During thepropagation step, the active monomer will react with additional monomersthat attach to the growing polymer chain. Finally, termination can occureither by recombination or by disproportionation.

-   -   Initiation        Initiator+h _(v) →R ⁻        R ⁻ +M→RM ⁻    -   Propagation        RM _(n) ⁻ +M _(n) →RM _(n+1) ⁻    -   Termination        -   combination            RM _(n) ⁻ +M _(m) R→RM _(n) M _(m) R        -   disproportionation            RM _(n) ⁻ +M _(m) R→RM _(n) +M _(m) R

In example embodiments, 3D formed objects generated by the processesoutlined herein may contain the following chemical products after theobject is created:

-   -   (1) Latent unreacted photoinitiator—photoinitiator is rarely        100% consumed during photopolymerization, therefore the product        will typically contain unreacted photoinitiators embedded        throughout the solid object:    -   (2) Photoinitiator by-products covalently attached to the        polymer network.

In example embodiments, photoinitiators may include the following:

(a) Benzoyl-Chromophore Based: These systems take the form

where “R” is any number of other atoms, including H, O, C, N, S. Theseinitiators cleave to form:

Where • represents a free radical. Either of these components may go onto initiate polymerization and will therefore be covalently bound to thepolymer network.

An example of such an initiator is shown below

(b) Morpholino and Amino Ketones. These systems take the form:

where “R” is any number of other atoms including H, O, C, N, S. Theseinitiators cleave to form

Where • represents a free radical. Either of these components may go onto initiate polymerization and will therefore be covalently bound to thepolymer network.

An example of such an initiator is shown below

(c) Benzoyl Phosphine Oxide. These systems take the form

where “R” is any number of other atoms including H, O, C, N, S. Theseinitiators cleave to form

Where • represents a free radical. Either of these components may go onto initiate polymerization and will therefore be covalently bound to thepolymer network.

An example of such an initiator is shown below

(d) Amines.

Many photoinitiators may be used in combination with amines. Here thephotoinitiators in the excited state serve to abstract a hydrogen atomfrom the amine, thus generating an active radical. This radical can goon to initiator polymerization and will therefore become incorporatedinto the formed polymer network. This process is outlined below:

Either of these active species can go on to form an active polymer chainresulting in the structures below R

(e) Other Systems.

Other types of photoinitiators that may be used to generate suchmaterials and therefore will generate fragments which are covalentlyattached to the formed polymer network include: triazines, ketones,peroxides, diketones, azides, azo derivatives, disulfide derivatives,disilane derivatives, thiol derivatives, diselenide derivatives,diphenylditelluride derivatives, digermane derivatives, distannanederivatives, carob-germanium compounds, carbon-silicon derivatives,sulfur-carbon derivatives, sulfur-silicon derivatives, peresters,Barton's ester derivatives, hydroxamic and thiohydroxamic acids andesters, organoborates, organometallic compounds, titanocenes, chromiumcomplexes, alumate complexes, carbon-sulfur or sulfur-sulfur inifertercompounds, oxyamines, aldehydes, acetals, silanes,phosphorous-containing compounds, borane complexes, thioxanthonederivatives, coumarins, anthraquinones, fluorenones, ferrocenium salts.

(f) Detection.

Detection of the unique chemical fingerprint of photoinitiator fragmentsin a cured polymer object can be accomplished by a number ofspectroscopic techniques. Particular techniques useful alone or incombination include: UV-Vis spectroscopy, fluorescence spectroscopy,infrared spectroscopy, nuclear magnetic resonance spectroscopy, massspectrometry, atomic absorption spectroscopy, raman spectroscopy, andX-Ray photoelectron spectroscopy.

D. Example Properties of 3D Objects.

The structural properties of the 3D formed object may be selectedtogether with the properties of the materials from which the 3D objectis formed to provide a wide range of properties for the 3D object. Dualcure materials and methods described above in the present applicationmay be used to form complex shapes with desired materials properties toform a wide range of 3D objects.

In some embodiments, 3D formed objects may be rigid and have, forexample, a Young's modulus (MPa) in the range of about 800 to 3500 orany range subsumed therein, a Tensile Strength (MPa) in the range ofabout 30 to 100 or any range subsumed therein, and/or a percentelongation at break in the range of about 1 to 100 or any range subsumedtherein. Non-limiting examples of such rigid 3D formed objects mayinclude fasteners; electronic device housings; gears, propellers, andimpellers; wheels, mechanical device housings; tools and other rigid 3Dobjects.

In some embodiments, 3D formed objects may be semi-rigid and have, forexample, a Young's modulus (MPa) in the range of about 300-2500 or anyrange subsumed therein, a Tensile Strength (MPa) in the range of about20-70 or any range subsumed therein, and/or a percent elongation atbreak in the range of about 40 to 300 or 600 or any range subsumedtherein. Non-limiting examples of such rigid 3D formed objects mayinclude structural elements; hinges including living hinges; boat andwatercraft hulls and decks; wheels; bottles, jars and other containers;pipes, liquid tubes and connectors and other semi-rigid 3D objects.

In some embodiments, 3D formed objects may be elastomeric and have, forexample, a Young's modulus (MPa) in the range of about 0.5-40 or anyrange subsumed therein, a Tensile Strength (MPa) in the range of about0.5-30 or any range subsumed therein, and/or a percent elongation atbreak in the range of about 50-1000 or any range subsumed therein.Non-limiting examples of such rigid 3D formed objects may includefoot-wear soles, heels, innersoles and midsoles; bushings and gaskets;cushions; electronic device housings and other elastomeric 3D objects.

In some example embodiments, the process of fabricating the product maybe paused or interrupted one or more times, to change the polymerizableliquid. In example embodiments, 3D formed objects may include multiplematerials (which may, for example, be a thermoplastic or thermosetpolyurethane, polyurea, or copolymer thereof) with different tensilestrengths. While a fault line or plane may be formed in the intermediateby the interruption, if the subsequent polymerizable liquid is, in itssecond cure material, reactive with that of the first, then the twodistinct segments of the intermediate will cross-react and covalentlycouple to one another during the second cure (e.g., by heating ormicrowave irradiation). Thus, for example, any of the materialsdescribed herein may be sequentially changed to form a product havingmultiple distinct segments with different tensile properties, whilestill being a unitary product with the different segments covalentlycoupled to one another. In some embodiments, a 3D object may be formedwith a plurality of regions with different materials and properties. Forexample, a 3D formed object could have one or more regions formed from afirst material or first group of one or more materials having a TensileStrength (MPa) in the range of about 30-100 or any range subsumedtherein, and/or one or more regions formed from a second material orsecond group of one or more materials having a Tensile Strength (MPa) inthe range of about 20-70 or any range subsumed therein and/or one ormore regions formed from a third material or third group of one or morematerials having a Tensile Strength (MPa) in the range of about 0.5-30or any range subsumed therein or any combination of the foregoing. Forexample, the 3D object could have from 1-10 or more different regions(or any range subsumed therein) with varying tensile strength selectedfrom any of the materials and tensile strengths described above. Forexample, a hinge can be formed, with the hinge comprising a rigidsegment, coupled to a second elastic segment, coupled to a third rigidsegment, by sequentially changing polymerizable liquids (e.g., fromamong those described in examples 19-60 above) during the formation ofthe three-dimensional intermediate. A shock absorber or vibrationdampener can be formed in like manner, with the second segment beingeither elastic or semi-rigid. A unitary rigid funnel and flexible hoseassembly can be formed in like manner.

E. Additional Examples of 3D Objects.

The above methods, structures, materials, compositions and propertiesmay be used to 3D print a virtually unlimited number of products.Examples include, but are not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,catheters, bladder, breast implants, testicle implants, pectoralimplants, eye implants, contact lenses, dental aligners, microfluidics,seals, shrouds, and other applications requiring high biocompatibility,functional structures, microneedle arrays, fibers, rods, waveguides,micromechanical devices, microfluidic devices; fasteners; electronicdevice housings; gears, propellers, and impellers; wheels, mechanicaldevice housings; tools; structural elements; hinges including livinghinges; boat and watercraft hulls and decks; wheels; bottles, jars andother containers; pipes, liquid tubes and connectors; foot-ware soles,heels, innersoles and midsoles; bushings, o-rings and gaskets; shockabsorbers, funnel/hose assembly, cushions; electronic device housings;shin guards, athletic cups, knee pads, elbow pads, foam liners, paddingor inserts, helmets, helmet straps, head gear, shoe cleats, gloves,other wearable or athletic equipment, brushes, combs, rings, jewelry,buttons, snaps, fasteners, watch bands or watch housings, mobile phoneor tablet casings or housings, computer keyboards or keyboard buttons orcomponents, remote control buttons or components, auto dashboardcomponents, buttons, dials, auto body parts, paneling, other automotive,aircraft or boat parts, cookware, bakeware, kitchen utensils, steamersand any number of other 3D objects. The universe of useful 3D productsthat may be formed is greatly expanded by the ability to impart a widerange of shapes and properties, including elastomeric properties,through the use of multiple methods of hardening such as dual cure wherea shape can be locked-in using continuous liquid interphase printing andsubsequent thermal or other curing can be used to provide elastomeric orother desired properties. Any of the above described structures,materials and properties can be combined to form 3D objects includingthe 3D formed products described above. These are examples only and anynumber of other 3D objects can be formed using the methods and materialsdescribed herein.

VII. Washing of Intermediate Prior to Second Cure.

When desired, washing of the intermediate may be carried out by anysuitable technique, aided with any suitable apparatus, including but notlimited to those described in U.S. Pat. No. 5,248,456, the disclosure ofwhich is incorporated herein by reference.

Wash liquids that may be used to carry out the present inventioninclude, but are not limited to, water, organic solvents, andcombinations thereof (e.g., combined as co-solvents), optionallycontaining additional ingredients such as surfactants, chelants(ligands), enzymes, borax, dyes or colorants, fragrances, etc.,including combinations thereof. The wash liquid may be in any suitableform, such as a solution, emulsion, dispersion, etc.

Examples of organic solvents that may be used as a wash liquid, or as aconstituent of a wash liquid, include, but are not limited to, alcohol,ester, dibasic ester, ketone, acid, aromatic, hydrocarbon, ether,dipolar aprotic, halogenated, and base organic solvents, includingcombinations thereof. Solvents may be selected in based, in part, ontheir environmental and health impact (see, e.g., GSK Solvent SelectionGuide 2009).

Examples of alcohol organic solvents that may be used in the presentinvention include, but are not limited to, aliphatic and aromaticalcohols such as 2-ethyl hexanol, glycerol, cyclohexanol, ethyleneglycol, propylene glycol, di-propylene glycol, 1,4-butanediol, isoamylalcohol, 1,2-propanediol, 1,3-propanediol, benzyl alcohol, 2-pentanol,1-butanol, 2-butanol, methanol, ethanol, t-butanol, 2-propanol,1-propanol, 2-methoxyethanol, tetrahydrofuryl alcohol, benzyl alcohol,etc., including combinations thereof. In some embodiments, a C1-C6 orC1-C4 aliphatic alcohol is preferred.

Examples of ester organic solvents that may be used to carry out thepresent invention include, but are not limited to, t-butyl acetate,n-octyl acetate, butyl acetate, ethylene carbonate, propylene carbonate,butylenes carbonate, glycerol carbonate, isopropyl acetate, ethyllactate, propyl acetate, dimethyl carbonate, methyl lactate, ethylacetate, ethyl propionate, methyl acetate, ethyl formate etc., includingcombinations thereof.

Examples of dibasic ester organic solvents include, but are not limitedto, dimethyl esters of succinic acid, glutaric acid, adipic acid, etc.,including combinations thereof.

Examples of organic ketone organic solvents that may be used to carryout the present invention include, but are not limited to,cyclohexanone, cyclopentanone, 2-pentanone, 3-pentanone, methylisobutylketone, acetone, methylethyl ketone, etc., including combinationsthereof.

Examples of acid organic solvents that may be used to carry out thepresent invention include, but are not limited to, propionic acid,acetic anhydride, acetic acid, etc., including combinations thereof.

Examples of aromatic organic solvents that may be used to carry out thepresent invention include, but are not limited to, mesitylene, cumene,p-xylene, toluene, benzene, etc., including combinations thereof.

Examples of hydrocarbon (i.e., aliphatic) organic solvents that may beused to carry out the present invention include, but are not limited to,cis-decalin, ISOPAR G, isooctane, methyl cyclohexane, cyclohexane,heptane, pentane, methylcyclopentane, 2-methylpentane, hexane, petroleumspirit, etc., including combinations thereof.

Examples of ether organic solvents that may be used to carry out thepresent invention include, but are not limited to, di(ethylene glycol),ethoxybenzene, tri(ethylene glycol), sulfolane, DEG monobutyl ether,anisole, diphenyl ether, dibutyl ether, t-amyl methyl ether,t-butylmethyl ether, cyclopentyl methyl ether, t-butyl ethyl ether,2-methyltetrahydrofuran, diethyl ether, bis(2-methoxyethyl) ether,dimethyl ether, 1,4-dioxane, tetrahydrofuran, 1,2-dimethoxyethane,diisopropyl ether, etc., including combinations thereof.

Examples of dipolar aprotic organic solvents that may be used to carryout the present invention include, but are not limited to,dimethylpropylene urea, dimethyl sulphoxide, formamide, dimethylformamide, N-methylformamide, N-methyl pyrrolidone, propanenitrile,dimethyl acetamide, acetonitrile, etc., including combinations thereof.

Examples of halogenated organic solvents that may be used to carry outthe present invention include, but are not limited to,1,2-dichlorobenzene, 1,2,4-trichlorobenzene, chlorobenzene,trichloroacetonitrile, chloroacetic acid, trichloroacetic acid,perfluorotoluene, perfluorocyclohexane, carbon tetrachloride,dichloromethane, perfluorohexane, fluorobenzene, chloroform,perfluorocyclic ether, trifluoracetic acid, trifluorotoluene,1,2-dichloroethane, 2,2,2-trifluoroethanol, etc., including combinationsthereof.

Examples of base organic solvents that may be used to carry out thepresent invention include, but are not limited to, N,N-dimethylaniline,triethylamine, pyridine, etc., including combinations thereof.

Examples of other organic solvents that may be used to carry out thepresent invention include, but are not limited to, nitromethane, carbondisulfide, etc., including combinations thereof.

Examples of surfactants include, but are not limited to, anionicsurfactants (e.g., sulfates, sulfonatse, carboxylates, and phosphateesters), cationic surfactants, zwitterionic surfactants, nonionicsurfactants, etc., including combinations thereof. Common examplesinclude, but are not limited to, sodium stearate, linearalkylbenzenesulfonates, lignin sulfonates, fatty alcohol ethoxylates,alkylphenol ethoxylates, etc., including combinations thereof. Numerousexamples additional examples of suitable surfactants are known, some ofwhich are described in U.S. Pat. Nos. 9,198,847, 9,175,248, 9,121,000,9,120,997, 9,095,787, 9,068,152, 9,023,782, and 8,765,108.

Examples of chelants (chelating agents) include, but are not limited to,ethylenediamine tetraacetic acid, phosphates, nitrilotriacetic acid(NTA), citrates, silicates, and polymers of acrylic and maleic acid.

Examples of enzymes that may be included in the wash liquid include, butare not limited to, proteases, amylases, lipases, cellulases, etc.,including mixtures thereof. See. e.g., U.S. Pat. Nos. 7,183,248,6,063,206, In some embodiments, the wash liquid can be an aqueoussolution of ethoxylated alcohol, sodium citrate, tetrasodiumN,N-bis(carboxymethyl)-L-glutamate, sodium carbonate, citric acid, andisothiazolinone mixture. One particular example thereof is SIMPLE GREEN®all purpose cleaner (Sunshine Makers Inc., Huntington Beach, Calif. USA)used per se or mixed with additional water.

In some embodiments, the wash liquid can be an aqueous solutioncomprised of 2-butoxyethanol, sodium metasilicate, and sodium hydroxide.One particular example thereof is PURPLE POWER™ degreaser/cleaner (AikenChemical Co., Greenville, S.C., USA), used per se or mixed withadditional water.

In some embodiments, the wash liquid can be ethyl lactate, alone or witha co-solvent. One particular example thereof is BIO-SOLV™ solventreplacement (Bio Brands LLC. Cinnaminson, N.J. USA), used per se ormixed with water.

In some embodiments, the wash liquid consists of a 50:50 (volume:volume)solution of water and isopropanol.

Examples of hydrofluorocarbon solvents that may be used to carry out thepresent invention include, but are not limited to,1,1,1,2,3,4,4,5,5-decafluoropentane (Vertrel XF, DuPont Chemours),1,1,1,3,3-Pentafluoropropane, 1,1,1,3,3-Pentafluorobutane, etc.

Examples of hydrochlorofluorocarbon solvents that may be used to carryout the present invention include, but are not limited to,3,3-Dichloro-1,1,1,2,2-pentafluoropropane,1,3-Dichloro-1,1,2,2,3-pentafluoropropane, 1,1-Dichloro-1-fluoroethane,etc., including mixtures thereof.

Examples of hydrofluorether solvents that may be used to carry out thepresent invention include, but are not limited to, methylnonafluorobutyl ether (HFE-7100)), methyl nonafluoroisobutyl ether(HFE-7100), ethyl nonafluorobutyl ether (HFE-7200), ethylnonafluoroisobutyl ether (HFE-7200),1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, etc., includingmixtures thereof. Commercially available examples of this solventinclude Novec 7100 (3M), Novec 7200 (3M).

Examples of volatile methylsiloxane solvents that may be used to carryout the present invention include, but are not limited to,hexamethyldisiloxane (OS-10. Dow Corning), octamethyltrisiloxane (OS-20,Dow Corning), decamethyltetrasiloxane (OS-30. Dow Corning), etc.,including mixtures thereof.

In some embodiments, the wash liquid comprises an azeotropic mixturecomprising, consisting of, or consisting essentially of a first organicsolvent (e.g. a hydrofluorocarbon solvent, a hydrochlorofluorocarbonsolvent, a hydrofluorether solvent, amethylsiloxane solvent, orcombination thereof; e.g., in an amount of from 80 or 85 to 99 percentby weight) and a second organic solvent (e.g., a C1-C4 or C6 alcoholsuch as methanol, ethanol, isopropanol, tert-butanol, etc.; e.g., in anamount of from 1 to 15 or 20 percent by weight). Additional ingredientssuch as surfactants or chelants may optionally be included. In someembodiments, the azeotropic wash liquid may provide superior cleaningproperties, and/or enhanced recyclability, of the wash liquid.Additional examples of suitable azeotropic wash liquids include, but arenot limited to, those set forth in U.S. Pat. Nos. 6,008,179; 6,426,327;6,753,304; 6,288,018; 6,646,020; 6,699,829; 5,824,634; 5,196,137;6,689,734; and 5,773,403, the disclosures of which are incorporated byreference herein in their entirety.

When the wash liquid includes ingredients that are not desired forcarrying into the further curing step, in some embodiments the initialwash with the wash liquid can be followed with a further rinsing stepwith a rinse liquid, such as water (e.g., distilled and/or deionizedwater), or a mixture of water and an alcohol such as isopropanol.

Embodiments of the present invention are explained in greater detail inthe following non-limiting examples.

Example 1 A Flexible, “PVC-Like” Photo-Curable Polyurethane

This example describes dual cure polyurethane resins that producematerials and products having physical properties similar to that ofplasticized PVC.

The material is made by combining a part A with a part B, photo-curingthe mixture to solidify it's shape, and then baking it at a certaintemperature to access the desired final properties. Below is a sampleformulation:

WEIGHT REACTANT (g) % WT. PART A ABPU-25 22.4 48.20937% IBMA 5.612.08355% LMA 13.45 28.94714% TMPTMA 0.27  0.58260% TPO 0.594  1.27841%WIKOFF BLACK 0.12 0.258264% PART B PACM 4.03  8.67338%

ABPU-25: this component is an acrylate blocked polyurethane. It containsa mixture of two oligomers. One is a 650 Da diol, poly(tetramethyleneoxide) [PTMO-650] capped with methylene bis(4-cyclohexylisocyanate)[HMDI] that has been capped once more with 2-(tert-butylamino)ethylmethacrylate [TBAEMA]. The second oligomer is TBAEMA capped HMDI. Thefinal stoichiometric ratio of TBAEMA:HMDI:PTMO is 3.4:2.7:1.

IBMA: isobornyl methacrylate, reactive diluents.

LMA: lauryl methacrylate, reactive diluents.

TMPTMA: trimethylolpropane trimethacrylate, crosslinker.

TPO: diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, photo-initiator.

Wikoff Black: dispersion of black pigment.

PACM: 4,4′-methylenebiscyclohexylamine, chain extender.

Part A is synthesized by adding all of the individual components into acontainer and mixing until homogeneous. It is easiest to make a stocksolution using one of the reactive diluents (LMA for example) and thephotoinitiator, which is a powder. This stock solution can be added tothe ABPU and the other components and makes it easier to incorporate thephoto-initiator.

Part B can be added directly to part A in a 1:22 ratio by weight. Onceboth parts have been mixed thoroughly in an orbital or overhead mixerthe liquid resin can be photo-cured.

After photo-curing the solid part may be washed in a solution ofisopropyl alcohol or Green Power Chemical Rapid Rinse to clean thesurface of any un-cured material. The part may be dried by patting downwith a towel or with the use of compressed air.

After drying, the part should be placed onto a non-stick pan and placedinto an oven at 120 degrees Celsius for up to 4 hours. After baking thepart should be placed on a counter-top to cool down. Let the part sitout for at least 24 hours before use.

Example 2 Representative Polyurethane Products Produced from Dual-CureMaterials

Polymerizable materials as described in the examples, or detaileddescription, above (or variations thereof that will be apparent to thoseskilled in the art) provide products with a range of different elasticproperties. Examples of those ranges of properties, from rigid, throughsemi-rigid (rigid and flexible), to flexible, and to elastomeric.Particular types of products that can be made from such materialsinclude but are not limited to those given in Table 32 below. Theproducts may contain reacted photoinitiator fragments (remnants of thefirst cure forming the intermediate product) when produced by someembodiments of methods as described above. It will be appreciated thatthe properties may be further adjusted by inclusion of additionalmaterials such as fillers and/or dyes, as discussed above.

The properties of the product, as characterized by the columns set forthin Table 1, can be influenced in a variety of ways.

In general, increasing the amount of amount of hard segment in thepolymer as compared to soft segment in the polymer will favor theproduction of more rigid, or rigid and flexible, materials. In onespecific example, increasing the amount of TBAEMA will increase theamount of hard segment, and will favor the production of more rigid, orrigid and flexible, materials.

Blending the constituents of the polymerizable liquid to generate morephases (e.g., 2 or 3) in the final polymerized product will tend tofavor the production of more resilient final products. For example, insome embodiments, a blend that generates 1 phase in the product willfavor the production of a rigid, or rigid and flexible, material, whilea blend that generates three phases in the material will, in someembodiments, favor the production of a flexible or elastomeric product.

Washing of the intermediate, and choice of wash liquid, can be used toinfluence the properties of the product. For example, a wash liquid thatsolubilizes a chain extender in the intermediate product and extractschain extender from the intermediate may soften the material, and favorthe production of less rigid products.

Altering the ratio of constituents that participate in the first curingstep, as compared to the constituents that participate in the secondcuring step, may also be used to alter the properties of the resultingproduct.

The inclusion of a filler in the resin, and the choice of filler (e.g.,silica, tougheners such as core-shell rubbers, etc.) may be used tochange the properties of the final product.

TABLE 1 Polyurethane Products by Properties and Example Products² Rigidand Flexible (Semi- Rigid Rigid) Flexible Elastomeric Young's  800-3500 300-2500  25-250 0.5-40  Modulus (MPa) Tensile  30-100 20-70  3-700.5-30  Strength (MPa) % Elongation  1-100 40-300 or 600 100-175 50-1000 at Break Phase(s) of 1 or 2 1 or 2 1, 2, or 3 2 or 3 material¹Non-limiting Fasteners; Structural Automotive Foot-ware soles, Exampleelectronic device elements; hinges interior parts heels, innersolesProducts housings; gears, including living (handles, and midsoles;propellers, and hinges; boat and dashboards, bushings and impellers;wheels, watercraft hulls etc.); toys; gaskets; cushions; mechanical anddecks; wheels; figurines, etc. electronic device device housings;bottles, jars and housings, etc. tools, etc. other containers; pipes,liquid tubes and connectors, etc. ¹The number of phases in the productmaterial corresponds directly to the number of peaks the materialexhibits by dynamic mechanical analysis, such as with a Seiko Exstar6000 dynamic mechanical analyzer. Where the material is a composite of amatrix polymer and a filler, the number of phases in this row refers tothe number of phases of the matrix polymer. ²In the table above, thefollowing general terms and phrases include the following non-limitingspecific examples: “Fastener” includes, but is not limited to, nuts,bolts, screws, expansion fasteners, clips, buckles, etc, “Electronicdevice housing” includes, but is not limited to, partial and completecell phone housings, tablet computer housings, personal computerhousings, electronic recorder and storage media housings, video monitorhousings, keyboard housings, etc., “Mechanical device housing” includes,but is not limited to, partial and complete gear housings, pumphousings, motor housings, etc. “Structural elements” as used hereinincludes, but is not limited to, shells, panels, rods, beams (e.g.,I-beams, U-beams, W-beams, cylindrical beams, channels, etc), struts,ties, etc., for applications including architectural and building, civilengineering, automotive and other transportation (e.g., automotive bodypanel, hood, chassis, frame, roof, bumper, etc.), etc. “Tools” includes,but is not limited to, impact tools such as hammers, drive tools such asscrewdrivers, grasping tools such as pliers, etc., including componentparts thereof (e.g., drive heads, jaws, and impact heads). “Toys”includes single unitary formed items or component parts thereof,examples of which include but are not limited to model vehicles(including airplanes, rockets, space ships, automobiles, trains), dollsand figurines (including human figurines, animal figurines, robotfigurines, fantasy creature figurines, etc.), etc., including compositesthereof and component parts thereof.

Example 4 Azeotropic Wash Liquids

There is a significant advantage to using azeotropes to clean parts. Insome embodiments, a blend of 95% by weight of Vertrel XMdecafluoropentane and 5% by weight of methanol cleans intermediateobjects formed from “dual cure” polyurethane resins as described above,and standard “single cure” prototyping resins, very well. Without theazeotropic component there is not sufficient hydrogen bonding or polarforces to satisfactorily remove residual resin on the surface of theobject (per Hansen Solubility Parameters).

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

We claim:
 1. A method of forming a three-dimensional object, comprising:(a) providing a carrier and a fill level, and optionally an opticallytransparent member having a build surface defining said fill level, saidcarrier and said fill level having a build region therebetween; (b)filling said build region with a polymerizable liquid, saidpolymerizable liquid comprising a mixture of (i) a light polymerizableliquid first component, and (ii) a second solidifiable component that isdifferent from said first component; (c) irradiating said build regionwith light, to form a solid polymer scaffold from said first componentand also advancing said carrier away from said build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, said three-dimensional object and containing said secondsolidifiable component carried in said scaffold in unsolidified and/oruncured form; (d) washing said three-dimensional intermediate with awash liquid; and (e) subsequent to said irradiating step and saidwashing step, heating said second solidifiable component in saidthree-dimensional intermediate to form said three-dimensional object. 2.The method of claim 1, wherein said wash liquid comprises an aqueouswash liquid.
 3. The method of claim 1, wherein said wash liquidcomprises an organic solvent.
 4. The method of claim 3, wherein saidorganic solvent is selected from the group consisting of alcohol, ester,dibasic ester, ketone, acid, aromatic, hydrocarbon, ether, dipolaraprotic, halogenated, and base organic solvents, and combinationsthereof.
 5. The method of claim 3, wherein said organic solventcomprises a hydrofluorocarbon, a hydrofluoroether, or a combinationthereof.
 6. The method of claim 3, wherein said organic solventcomprises an azeotropic mixture comprised of at least a first organicsolvent and a second organic solvent.
 7. The method of claim 1, whereinsaid wash liquid further comprises a surfactant, chelant, enzyme, or acombination thereof.
 8. The method of claim 1, wherein said secondsolidifiable component comprises: (i) a polymerizable liquid solubilizedin or suspended in said first component; (ii) a polymerizable solidsuspended in said first component; (iii) a polymerizable solidsolubilized in said first component; or (iv) a polymer solubilized insaid first component.
 9. The method of claim 1, wherein saidthree-dimensional object comprises a polymer blend, interpenetratingpolymer network, semi-interpenetrating polymer network, or sequentialinterpenetrating polymer network formed from said first component andsaid second solidifiable component.
 10. The method of claim 1, whereinsaid second solidifiable component comprises the precursors to asilicone resin, an epoxy resin, a cyanate ester resin, or a naturalrubber.
 11. The method of claim 1, wherein said second solidifiablecomponent comprises the precursors to a polyurethane, polyurea, orcopolymer thereof.
 12. The method of claim 1, wherein said heating step(e) is carried out under conditions in which said solid polymer scaffolddegrades and forms a constituent necessary for the polymerization ofsaid second solidifiable component.
 13. The method of claim 1, whereinsaid second solidifiable component comprises precursors to apolyurethane, polyurea, or copolymer thereof, a silicone resin, aring-opening metathesis polymerization resin, a click chemistry resin,or a cyanate ester resin.
 14. The method of claim 1, wherein saidirradiating and/or said advancing steps are carried out while alsoconcurrently: (i) continuously maintaining a dead zone of polymerizableliquid in contact with said build surface, and (ii) continuouslymaintaining a gradient of polymerization zone between said dead zone andsaid solid polymer and in contact with each thereof, said gradient ofpolymerization zone comprising said first component in partially curedform.
 15. The method of claim 1, wherein said first component comprisesmonomers and/or prepolymers comprising reactive end groups selected fromthe group consisting of acrylates, methacrylates, α-olefins, N-vinyls,acrylamides, methacrylamides, styrenics, epoxides, thiols, 1,3-dienes,vinyl halides, acrylonitriles, vinyl esters, maleimides, and vinylethers.
 16. The method of claim 1, wherein said second solidifiablecomponent comprises monomers and/or prepolymers comprising reactive endgroups selected from the group consisting of: epoxy/amine,epoxy/hydroxyl, oxetane/amine, oxetane/alcohol, isocyanate/hydroxyl,isocyanate/amine, isocyanate/carboxylic acid, cyanate ester,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H,Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde, amine/aldehyde,hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast, alkyne/azide,click chemistry reactive groups, alkene/sulfur, alkene/thiol,alkyne/thiol, hydroxyl/halide, isocyanate/water, Si—OH/hydroxyl,Si—OH/water, Si—OH/Si—H, Si—OH/Si—OH, perfluorovinyl, diene/dienophiles,olefin metathesis polymerization groups, olefin polymerization groupsfor Ziegler-Natta catalysis, and ring-opening polymerization groups andmixtures thereof.
 17. The method of claim 1, wherein the wash liquidcomprises alcohol.
 18. The method of claim 17, wherein the alcoholcomprises isopropanol.
 19. The method of claim 1, wherein the washliquid comprises a mixture of isopropanol and water.
 20. The method ofclaim 1, wherein the second solidifiable component comprises apolymerizable liquid suspended in the first component.
 21. The method ofclaim 1, wherein the second solidifiable component comprises apolymerizable solid suspended in the first component.
 22. The method ofclaim 1, wherein said three-dimensional object comprises aninterpenetrating polymer network formed from said first component andsaid second solidifiable component.
 23. The method of claim 1, whereinsaid solid polymer scaffold is discontinuous.
 24. The method of claim 1,wherein said solid polymer scaffold comprises a lattice.
 25. The methodof claim 1, wherein said first component comprises monomers and/orprepolymers comprising reactive end groups selected from the groupconsisting of acrylates and methacrylates.
 26. The method of claim 1,wherein said second solidifiable component comprises monomers and/orprepolymers comprising reactive end groups selected from the groupconsisting of: isocyanate/hydroxyl and isocyanate/amine.
 27. The methodof claim 1, wherein said three-dimensional object is elastomeric.
 28. Amethod of forming a three-dimensional object, comprising: (a) providinga carrier and a fill level, and optionally an optically transparentmember having a build surface defining said fill level, said carrier andsaid fill level having a build region therebetween; (b) filling saidbuild region with a polymerizable liquid, said polymerizable liquidcomprising a mixture of (i) a light polymerizable liquid firstcomponent, and (ii) a second solidifiable component that is differentfrom said first component, wherein said second solidifiable componentcomprises the precursors to a cyanate ester resin; (c) irradiating saidbuild region with light, to form a solid polymer scaffold from saidfirst component and also advancing said carrier away from said buildsurface to form a three-dimensional intermediate having the same shapeas, or a shape to be imparted to, said three-dimensional object andcontaining said second solidifiable component carried in said scaffoldin unsolidified and/or uncured form; (d) washing said three-dimensionalintermediate with a wash liquid, wherein said wash liquid comprises anorganic solvent; and (e) subsequent to said irradiating step and saidwashing step, heating said second solidifiable component in saidthree-dimensional intermediate to form said three-dimensional object.29. The method of claim 28, wherein the organic solvent comprises analcohol.
 30. The method of claim 29, wherein the alcohol comprisesisopropanol, propylene glycol, or a combination thereof.
 31. A method offorming a three-dimensional object, comprising: (a) providing a carrierand a fill level, and optionally an optically transparent member havinga build surface defining said fill level, said carrier and said filllevel having a build region therebetween; (b) filling said build regionwith a polymerizable liquid, said polymerizable liquid comprising amixture of (i) a light polymerizable liquid first component, and (ii) asecond solidifiable component that is different from said firstcomponent, wherein said second solidifiable component comprises theprecursors to an epoxy resin; (c) irradiating said build region withlight, to form a solid polymer scaffold from said first component andalso advancing said carrier away from said build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, said three-dimensional object and containing said secondsolidifiable component carried in said scaffold in unsolidified and/oruncured form; (d) washing said three-dimensional intermediate with awash liquid, wherein said wash liquid comprises an organic solvent; and(e) subsequent to said irradiating step and said washing step, heatingsaid second solidifiable component in said three-dimensionalintermediate to form said three-dimensional object.
 32. The method ofclaim 31, wherein the organic solvent comprises a dibasic ester.
 33. Themethod of claim 32, wherein the dibasic ester comprises a dimethyl esterof adipic acid.
 34. The method of claim 31, wherein the organic solventcomprises an ether.
 35. The method of claim 34, wherein the organicsolvent comprises an alcohol.
 36. The method of claim 35, wherein thealcohol comprises isopropanol, propylene glycol, or a combinationthereof.
 37. A method of forming a three-dimensional object, comprising:(a) providing a carrier and a fill level, and optionally an opticallytransparent member having a build surface defining said fill level, saidcarrier and said fill level having a build region therebetween; (b)filling said build region with a polymerizable liquid, saidpolymerizable liquid comprising a mixture of (i) a light polymerizableliquid first component, and (ii) a second solidifiable component that isdifferent from said first component, wherein said second solidifiablecomponent comprises the precursors to a polyurethane, polyurea, orcopolymer thereof; (c) irradiating said build region with light, to forma solid polymer scaffold from said first component and also advancingsaid carrier away from said build surface to form a three-dimensionalintermediate having the same shape as, or a shape to be imparted to,said three-dimensional object and containing said second solidifiablecomponent carried in said scaffold in unsolidified and/or uncured form;(d) washing said three-dimensional intermediate with a wash liquid,wherein said wash liquid comprises an organic solvent; and (e)subsequent to said irradiating step and said washing step, heating saidsecond solidifiable component in said three-dimensional intermediate toform said three-dimensional object.
 38. The method of claim 37, whereinthe organic solvent comprises an ether.
 39. The method of claim 37,wherein the organic solvent comprises an alcohol.
 40. The method ofclaim 39, wherein the alcohol comprises isopropanol, propylene glycol,or a combination thereof.